Patent Publication Number: US-2006020230-A1

Title: Devices and methods for cervix measurement

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This is a continuation of application Ser. No. 10/924,411, filed Aug. 23, 2004, now allowed, which is a continuation of application Ser. No. 10/366,024 entitled “Devices and Methods for Cervix Measurement,” filed on Feb. 12, 2003, issued as U.S. Pat. No. 6,802,817, which is a continuation of application Ser. No. 09/877,986 entitled “Devices and Methods for Cervix Measurement,” filed on Jun. 8, 2001, issued as U.S. Pat. No. 6,524,259, the disclosures of which are expressly incorporated by reference. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates to medical devices and methods of using such devices. More particularly, the invention relates to instruments and methods to measure the length of the cervix in the fornix vaginae and the dilation of the cervix uteri.  
     BACKGROUND  
      Preterm labor, or labor before 37 weeks gestation, has been reported in 7 to 10 percent of all births but accounts for more than 85 percent of all perinatal complications and death. Rush et al.,  BMJ  2:965-8 (1976) and Villar et al.,  Res. Clin. Forums  16:9-33 (1994), which are both incorporated herein by reference. An inverse relationship between cervical length in the fornix vaginae and the risk of preterm labor has also been observed. Anderson et al.,  Am. J. Obstet. Gynecol.  163:859 (1990); Iams et al.,  N. Eng. J. Med.  334:567-72 (1996) and Heath et al., and  Ultrasound Obstet. Gynecol.  12:312-7 (1998), which all are incorporated herein by reference. Accordingly, many physicians find it useful to examine the cervix in the fornix vaginae as part of normal prenatal care in order to assess risk of preterm labor.  
      It has long been known that the cervix normally undergoes a series of physical and biochemical changes during the course of pregnancy, which enhance the ease and safety of the birthing process for the mother and baby. For example, in the early stages of labor the tissues of the cervical canal soften and become more pliable, the cervix shortens (effaces), and the circumference of the proximal end of the cervical canal begins to increase at the internal os. As labor progresses, growth of the cervical diameter propagates to the distal end of the cervical canal, toward the external os. In the-final stages of labor, the external os dilates allowing for the unobstructed passage of the fetus.  
      In addition to the physical and biochemical changes associated with normal labor, genetic or environmental factors, such as medical illness or infection, stress, malnutrition, chronic deprivation and certain chemicals or drugs can cause changes in the cervix. For example, it is well known that the in utero exposure of some women to diethylstilbestrol (DES) results in cervical abnormalities and in some cases gross anatomical changes, which leads to an incompetent cervix where the cervix matures, softens and painlessly dilates without apparent uterine contractions. An incompetent cervix can also occur where there is a history of cervical injury, as in a previous traumatic delivery, or as a result of induced abortion of the cervix is forcibly dilated to large diameters. Details of the incompetent cervix are discussed in Sonek, et al.,  Preterm Birth, Causes, Prevention and Management,  Second Edition, McGraw-Hill, Inc., (1993), Chapter 5, which is incorporated by reference herein.  
      Cervical incompetence is a well-recognized clinical problem. Several investigators have reported evidence of increased cervical os diameter as being consistent with cervical incompetence (see Brook et al.,  J. Obstet. Gynecol.  88:640 (1981); Michaels et al.,  Am. J. Obstet. Gynecol.  154:537 (1986); Sarti et al.,  Radiology  130:417 (1979); and Vaalamo et al.,  Acta Obstet. Gynecol. Scan  62:19 (1983), all of which are incorporated by reference herein). Internal os diameters ranging between 15 mm to 23 mm have been observed in connection with an incompetent cervix. Accordingly, a critical assessment in the diagnosis of an incompetent cervix involves measurement of the internal cervical os diameter.  
      There are also devices and methods to measure the diameter of the external cervical os. For example, cervical diameter can be manually estimated by a practitioner&#39;s use of his or her digits. Although an individual practitioner can achieve acceptable repeatability using this method, there is significant variation between practitioners due to the subjective nature of the procedure. To address these concerns, various monitoring and measuring devices and methods have been developed. For example, an instrument for measuring dilation of the cervix uteri is described in U.S. Pat. No. 5,658,295. However, this device is somewhat large, leading to a risk of injury to the fundus of the vagina or cervical os. Additionally, it is not disposable and requires repeated sterilization. Another device for measuring cervical diameter is described, for example, in U.S. Pat. No. 6,039,701. In one version, the device described therein has a loop element that is secured to the cervix. The loop expands or contracts with the cervix and a gauge is coupled to the loop for measuring changes in the loop dimension. Such changes can then be detected by electronic means. Accordingly, this device is rather complex and expensive to manufacture.  
      Even if a woman is found to have an apparently normal internal cervical os diameter, there may nonetheless be a risk for preterm labor and delivery. Currently, risk assessment for preterm delivery remains difficult, particularly among women with no history of preterm birth. However, the findings that preterm delivery is more common among women with premature cervical shortening or effacement suggest that measuring the length of the cervix would be predictive for preterm labor.  
      Currently, a physician has at least two options to measure the length of the cervix in the fornix vaginae. One such method involves serial digital examination of the cervix by estimating the length from the external cervical os to the cervical-uterine junction, as palpated through the vaginal fornix. Although this is useful for general qualitative analysis, it does not afford an easy nor accurate measurement of the length of the cervix from the external cervical os to the cervical-uterine junction (also described herein as the length of the cervix extending into the vagina) and, therefore, does not provide an accurate assessment of the risk of preterm labor. Despite the use of gloves, vaginal exams always carry with them the risk of transmitting infectious agents, especially to the fetal membranes, the lining and/or muscle of the uterus, or the fetus itself.  
      Another method involves real-time sonographic evaluation of the cervix. This method provides relatively quick and accurate cervical dimensions. However, it requires expensive equipment, highly skilled operators, as well as skill in interpretation of results, which are all subject to human error. Also, due to the expense of the procedure many women, especially those without proper health insurance, cannot afford to have a sonographic test performed.  
      It would be beneficial if there were an instrument a practitioner could use to measure the cervix quickly and accurately, and with little material expense. Although there are several instruments available for determining various dimensions of the uterus, there is no suitable instrument for measuring the length of the cervix in the fornix vaginae. For example, U.S. Pat. No. 4,016,867 describes a uterine caliper and depth gauge for taking a variety of uterine measurements, which although useful for fitting an intrauterine contraceptive device, is not capable of measuring the length of the cervix in the fornix vaginae due to interference by the caliper&#39;s wings. In fact, similar devices described in U.S. Pat. Nos.: 4,224,951; 4,489,732; 4,685,747; and 5,658,295 suffer from similar problems due to their use of expandable wings or divergable probe tips. These devices are also relatively sophisticated, making them expensive to manufacture and purchase. U.S. Pat. No. 3,630,190 describes a flexible intrauterine probe, which is particularly adapted to measuring the distance between the cervical os and the fundus of the uterus. The stem portion of the device has a plurality of annular ridges spaced apart from each other by a predetermined distance, preferably not more than one-half inch apart. However, this device is not adapted for accurately measuring the length of the cervix in the fornix vaginae because of the lack of an appropriate measuring scale and a stop for automatically recording the measurement.  
      Accordingly, there is currently no commercially available, quick, and inexpensive as well as accurate device to assess the risk of preterm labor by measuring the length of the cervix in the fornix vaginae. Therefore, many women at risk for preterm labor may be unaware of the risk to their pregnancy and their unborn child. If such a device were available, many more women would be better informed about the course of their pregnancy and would then be able to make better choices about becoming pregnant at all, or about managing their pregnancy to reduce the risk of preterm labor and injury to the unborn child.  
      Thus, there exists a need for a simple and inexpensive device that can be used to determine the length of the cervix in the fornix vaginae and, thus, predict the risk of preterm labor, as well as other conditions. There is also a need for such a device that can measure the dilation of the cervix uteri, to provide an overall assessment of the cervix and to determine the particular stage of labor. Ideally, the device should be adapted for use by a physician or obstetrician or even a trained nurse in the doctor&#39;s office or clinic. Preferably, the device should be disposable or capable of being sterilized. In addition, it is desirable that device record the measurement automatically. The present invention satisfies these needs and provides related advantages as well.  
     SUMMARY OF THE INVENTION  
      The present invention provides devices and methods for determining a dimension of a female reproductive organ.  
      In one aspect of the present invention, a device for determining a dimension of an organ may include a hollow member with a distal end, a proximal end, and a lumen therebetween, and a measurement member with a distal portion, a proximal portion, and a measurement scale disposed along the proximal portion, wherein the measurement member may be inserted into the lumen of the hollow member. The measurement scale of the measurement member may have a plurality of color-coded incremental markings. Additionally, the device may include a flange having a body offset substantially perpendicular to the hollow member, wherein the flange is attached to the distal end of the hollow member. A light element configured to emit light toward the distal end of the measurement member may also be provided on the device.  
      The light element of the device may comprise a light emitting component and an attachment means coupled to the light emitting component, wherein the attachment means is configured to secure the light element to the hollow member. In one embodiment, the attachment means comprises screws. In another embodiment, the attachment means comprises snap-on clips. When equipped with a light element, the device may also include a power source and a plurality of lead wires electrically coupling the light emitting component of the light element to the power source. In embodiments where the light element is disposed within the distal portion of the measurement member, the device may comprise a handle having an interior space, wherein the handle is attached to the proximal portion of the measurement member, a power source disposed within the interior space of the handle, and a plurality of lead wires attached to the power source and extending through the measurement member. In this embodiment, the lead wires electrically couple the light element with the power source.  
      The flange of the device may include a plurality of measurement markings on the body, and an opening suitable for advancement therethrough of the measurement member. The flange may be constructed of a substantially translucent material.  
      In another aspect of the present invention, a device for determining a dimension of an organ is provided that includes a hollow member having a distal end, a proximal end, and a lumen therebetween, and a measurement member having a distal portion, a proximal portion, and a measurement scale disposed along the proximal portion. The measurement member may be inserted into the lumen of the hollow member. The device may include a flange having a body offset substantially perpendicular from the hollow member and an opening for advancement of the measurement member therethrough. The flange may be attached to the distal end of the hollow member.  
      The device may also incorporate a light element disposed within the measurement member. In one embodiment, at least the distal portion of the measurement member is substantially translucent. The device may include a handle attached to the proximal portion of the measurement member and housing a power source, wherein the power source is coupled to the light element. Additionally, an outer sleeve may surround the handle. The outer sleeve may comprise an outer shell with an interior space having a proximal region and a distal region, and a resilient element within the proximal region of the interior space of the outer shell, wherein the handle is disposed in the distal region of the interior space of the outer shell.  
      In another aspect of the present invention, a device for determining a dimension of an organ is provided that may include a measurement member having a main body, a distal end extending substantially perpendicular to the main body, and a measurement scale along the member, and an outer member having a distal end, a proximal end, an open face, and a space for advancement therethrough of the measurement member. The outer member slidably engages the measurement member. The outer member may include a plurality of extensions parallel to the open face. Here, the extensions secure the measurement member within the space of the outer member. In another embodiment, the space of the outer member interlocks with the measurement member to slidably engage the measurement member.  
      The distal end of the measurement member may be a tear-drop shape. In another embodiment, the distal end of the measurement member may be a circular shape. The measurement member may be angular in cross-section. When the measurement member is angular in cross-section, the space of the outer member may be angular in cross-section and configured to slidably engage the measurement member. Alternatively, the outer member may be rectangular in cross-section.  
      Other objects and features of the present invention will become apparent from consideration of the following description taken in conjunction with the accompanying drawings. 
    
    
     DESCRIPTION OF THE DRAWINGS  
       FIG. 1  illustrates a device of the present invention having a measurement member, a hollow member, a flange, a locking mechanism, and a pin on the measurement member that travels within a slot on the hollow member.  
       FIG. 2  illustrates a flange suitable for incorporation with the devices of the present invention.  
       FIG. 3  illustrates a device as shown in  FIG. 1  and further including a detachable light emitting component attached to the circumference of the hollow member.  
       FIG. 4  illustrates a device of the present invention that includes a light emitting component integrated into the measurement member and located in the distal portion of the measurement member, and a handle that includes a power source for the light component.  
       FIG. 5  illustrates a device of the present invention having another embodiment of a locking mechanism.  
       FIG. 6   a ( i ) is a cross-sectional view of a device of the present invention that includes a hollow member and a measurement member having shapes configured for fixing the position of the measurement member without the need for an additional locking mechanism.  
       FIG. 6   a ( ii ) is a cross-sectional view of the device shown in  FIG. 6   a ( i ) showing a locked position of the hollow member and the measurement member.  
       FIG. 6   b  is a cross-sectional view of a device of the present invention incorporating a self-locking feature that includes a slot on the hollow member and a protrusion on the measurement member designed to engage a side wall of the slot in order to fix the position of the measurement member.  
       FIG. 6   c  is a cross-sectional view of a device of the present invention incorporating a self-locking feature that includes an opening on the hollow member, a fastening member inserted into the opening, and a flat face on the measurement member, wherein the fastening member is inserted into the opening and engages the flat face to fix the position of the measurement member.  
       FIG. 6   d  is a cross-sectional view of a device of the present invention incorporating a self-locking feature that includes a protrusion on the inner wall of the hollow member and a flat face on the measurement member, wherein the protrusion engages the flat face to fix the position of the measurement member.  
       FIG. 6   e  is a cross-sectional view of a device of the present invention incorporating a self-locking feature that includes an opening on the hollow member, a fastening member, such as, e.g., a screw, inserted into the opening, and an indentation extending longitudinally on the measurement member, wherein the fastening member is inserted into the opening and engages the indentation to fix the position of the measurement member.  
       FIG. 6   f  is a cross-sectional view of a device of the present invention incorporating a self-locking feature that includes a protrusion on the inner wall of the hollow member and an indentation extending longitudinally on the measurement member, wherein the protrusion engages the indentation to fix the position of the measurement member.  
       FIG. 6   g ( i )is a cross-sectional view of a device of the present invention incorporating a self-locking feature that includes an opening on the hollow member, a fastening member inserted into the opening, and two flat faces on the measurement member.  
       FIG. 6   g ( ii )is a cross-sectional view of the device shown in  FIG. 6   g ( ii ) along the line  6   g ( i ).  
       FIG. 7  is a device of the present invention that includes a pressure controlling sleeve surrounding the handle of the device.  
       FIG. 8  is a top plan view of another device of the present invention.  
       FIG. 8A  is a cross-sectional view of the device shown in  FIG. 8  along the line  8 A- 8 A.  
       FIG. 8B  is a cross-sectional view of the device shown in  FIG. 8  along the line  8 B- 8 B.  
       FIG. 8C  is a side view of the device shown in  FIG. 8 .  
       FIG. 8D  is a side view of a measurement member of the device shown in  FIG. 8 .  
       FIG. 9  is a top plan view of another embodiment of a device of the present invention.  
       FIG. 9A  is a cross-sectional view of the device of  FIG. 9  along the line  9 A- 9 A.  
       FIG. 9B  is a cross-sectional view of the device shown in  FIG. 9  along the line  9 B- 9 B.  
       FIG. 9C  is a side view of the device shown in  FIG. 9 .  
       FIG. 9D  is a side view of a measurement member of the device shown in  FIG. 9 . 
    
    
     DETAILED DESCRIPTION  
      The present invention provides various devices and methods for determining dimensions of female reproductive organs. For example, the device is particularly adapted for determining the length of the cervix in the fornix vaginae, which, as described above, is related to the risk of preterm labor in an individual. The device is also suited for determining the dilation of the cervix uteri, for predicting the risk of preterm labor or the particular stage of delivery. It is, however, contemplated herein, and also understood by those skilled in the art, that the invention can be used not only for determining various dimensions of female reproductive organs. For example, the invention is usable for determining the dimension of any body cavity or passageway where such a device would be insertable, such as a vagina, uterus, mouth, throat, nasal cavity, ear channel, rectum, and also to any cavity created and opened by surgery, for example, during chest, abdominal or brain surgery. The device is also preferably fabricated from relatively inexpensive materials and the measurement is quick to perform. Thus it allows the practitioner to repeat the test over time and therefore to more closely monitor a woman&#39;s pregnancy and risk for preterm labor. It is also contemplated that the device records the various measurements automatically, where the only input required by the practitioner is the proper insertion of the device into the body cavity or passageway. This is accomplished by the use of the flange to stop progression of the hollow member of the device while still allowing the measurement member to be advanced within the body.  
      As used herein the term “distal” refers to the end or portion of a device of the present invention, or a component thereof, that is adapted to be inserted first into a body cavity or passageway. As such, it will be that part of a device of the present invention furthest from the user while the device is inserted and progressed within the body cavity. Conversely, as used herein, the term “proximal” refers to the end or portion of the device nearest the user while the device is being inserted and progressed within the body cavity.  
      Turning to  FIG. 1 , a measuring device  100  of the present invention is illustrated. Measuring device  100  includes an elongated hollow member  104  having a distal region with a distal end, a proximal region with a proximal end, and a lumen extending between the distal and proximal ends. An elongated measurement member  102  is provided and is designed to be inserted into the hollow member  104 , and specifically into the lumen of the hollow member  104 . The measurement member  102  is elongate in shape and has a proximal region with a proximal end and a distal region with a distal end. The measurement member  102  is capable of being progressed coaxially within hollow member  104  both proximally and distally. In the illustrated embodiment of measuring device  100 , attached to the proximal end of the measurement member  102  is a handle  112 . In one embodiment, the handle  112  is molded from the same material as the measurement member  102 . Suitable materials and methods for the manufacture of the devices of the present invention are discussed herein. Alternatively, the handle  112  is a rubber or foam component that is fitted on to and over the proximal end of the measurement member  102 .  
      A measurement scale  118  is disposed along the proximal portion of the measurement member  102 . As used herein, the “measurement scale” refers to any number of a series of visual markings on the measurement member  102  at or near the proximal end, which relate a measurement or distance. In a particularly preferred embodiment, the measuring scale  118  includes a plurality of millimeter (mm) incremental markings and a plurality of centimeter (cm) incremental markings. As illustrated in  FIG. 1 , the measurement scale  118  includes relatively larger markings at 1, 2, 3, 4, and 5 cm in addition to a plurality of millimeter incremental markings between the centimeter markings. Further, a critical mark  120  is preferably present at approximately 2.5 cm. In one embodiment, the critical mark  120  is presented in a different color, such as, e.g., a red color, relative to the other incremental markings of the measurement scale  118 . The critical mark  120  is used to quickly notify a user of device  100  that a particular cervix length represents a greater risk of preterm delivery relative to longer cervix lengths. In another embodiment of the device  100 , the measurement scale  118  is coded into a plurality of regions. For example, in one implementation of this embodiment, the incremental markings less than 2 cm are coded in a first color, such as, e.g., red, the incremental markings from 2 to 3 cm are coded in a second color, such as, e.g., yellow, and the incremental markings from 3 to 5 cm are coded in a third color, such as, e.g., green. In this embodiment, the measurement scale  118  is color-coded into three regions that each visually represents the relative risks of preterm delivery for a cervix length falling within the respective region. In the above described example, for instance, the red zone indicates a shorter cervix, and therefore a higher risk of preterm delivery, than the yellow zone, which indicates a cervix length that reflects a higher risk of preterm delivery than the green zone. The measurement scale  118  is capable of being coded into regions based upon other distinguishing marks also, such as, e.g., a first region having a first type of marking for the measurement increments, a second region having a second type of marking for the measurement increments, and a third region having a third type of marking for the measurement increments. In other embodiments of device  100 , the incremental markings are in English measurements, such as inches and increments thereof, rather than the metric increments previously discussed.  
      As illustrated, the device  100  preferably includes a slot  114  oriented along the length-wise axis of hollow member  104 . Additionally, measurement member  102  includes a pin  116  disposed distally from the measurement scale  118 . In operation, measurement member  102  is placed within hollow member  104  such that pin  116  protrudes through slot 114. As a result, measurement member  102  is slidable within hollow member  104  while the rotation of measurement member  102  within hollow member  104  is significantly reduced.  
      In another embodiment of device  100  designed to reduce the amount of rotation of measurement member  102  while progressed within hollow member  104 , the measurement member  102  and hollow member  104  are not circular in shape. For example, both the measurement member  102  and hollow member  104  may be rectangular octagonal, square, or another shape having at least one angle such that any rotation of the measurement member  102  within hollow member  104  is substantially reduced and prevented by the angles of the measurement member  102  and hollow member  104 . A non-circular measurement member  102  and hollow member  104  may additionally include slot  114  on the hollow member  104  and pin  116  on the measurement member  102  to further decrease the amount of rotation between the two members.  
      Attached to the distal end of hollow member  104  is a flange  106  that is shaped for non-abrasive contact with tissue. As seen in  FIG. 1  and  FIG. 2 , which is an illustration of device  100  along the line  2 - 2 , the flange  106  is preferably flat and spherically or conically shaped. Alternatively, however, the flange  106  may be any other non-abrasive shape to reduce irritation and scraping of the cervical canal, fundus of the vagina or perforation of the fundus of the uterus. The main body of flange  106  is also preferably offset from the longitudinal axis of device  100 . Additionally, flange  106  includes an opening  105  through which measurement member  102  may be advanced distally after the flange  106  contacts a bodily surface. When the device  100  is used to measure the length of a cervix, the device  100  is advanced into the vagina until flange  106  is placed into contact with the end of the cervix at the external uterine opening. At this point, further forward progress of the hollow member  104  within the cervical canal or further within the body is prevented as a result of the contact between flange  106  and the end of the cervix at the external uterine opening. Since flange  106  is preferably offset from the longitudinal axis of device  100 , in one manner of operation optimal for measuring the length of the cervix, flange  106  is placed both in contact with the end of the cervix and also covering the external uterine opening. As a result, device  100  is oriented so that measurement member  102  is still able to be progressed within the fornix, rather than being advanced through the uterus, since the body of flange  106  is, with this method, covering the external uterine-opening. Subsequently, measurement member  102  is continued to be advanced through opening  105  of flange  106  until the distal end of the measurement member  102  contacts a wall of the body, such as, e.g., the anterior fornix. The length of the cervix is then measured by observing the position of the proximal end of the hollow member  104  along the measurement scale  118  of the measurement member  102 .  
      In another embodiment of the device  100 , the flange  106  further includes a plurality of measurement marks  122  that are, for example, usable for measuring the dilation of the cervix or external uterine opening. Here, the flange  106  is preferably manufactured from a substantially transparent or translucent material, such as plastic, so that the user is able to observe the flange  106  while the flange  106  is placed within the body. After the flange  106  contacts the external uterine opening, the user is able to measure the dilation of the cervix by comparing the size of the external uterine opening with the measurement marks  122  on the flange  106 . The measurement marks  122  may be metric, such as, e.g., incremental marks of millimeters, centimeters, or a combination thereof, or in English scale, such as, e.g., inches.  
      Preferably, the flange  106  is secured to the distal end of the hollow member  104  using a suitable attachment means, such as, e.g., an adhesive. Alternatively, the flange  106  may be formed as an integral component of the hollow member  104 .  
      Referring back to  FIG. 1 , a locking mechanism  124  is preferably located on the device  100  that allows a user to secure the measurement member  102  within the hollow member  104  after a measurement of a body part, such as, e.g., the length of the cervix, has been taken. The locking mechanism  124  preferably includes a collar  108  disposed around the circumference of the hollow member  104  and a locking knob  110  insertable into the collar  108 . In one embodiment, as shown in  FIG. 1 , the locking knob  110  resembles a fastening member, such as, e.g., a screw, with an enlarged area to facilitate the handling of the locking knob  110 . Preferably, the locking knob  110  is ergonomically designed so that it may also be used as a handle during the operation and positioning of the device  100  within the body. The collar  108  preferably includes an opening through which the locking knob  110  is capable of being inserted. Additionally, in this embodiment, the hollow member  104  also includes an opening through which the locking knob  110  is inserted after the locking knob  110  is inserted into the collar  108 . For example, after a measurement of a body part is taken with the device  100 , a user may lock the position of the measurement member  102  within the hollow member  104 , and therefore the position of the proximal end of the hollow member  104  along the measurement scale  118  of the measurement member  102 , by ensuring that the openings of the collar  108  and the hollow member  104  are aligned and then inserting the locking knob  110  through both openings simultaneously. The locking knob  110  is then threaded through the collar  108  and the hollow member  104  until the locking knob  110  engages the measurement member  102 . Once the locking knob  110  engages the measurement member  102 , the locking knob  110  is tightened so that movement of the measurement member  102  proximally or distally within the hollow member  104  is prevented. In another embodiment, rather than having an opening on the hollow member  104  for the locking knob  110 , the hollow member  104  includes a deformable region around the circumference of the hollow member  104  at the approximate region where the locking mechanism  124  is placed. Here, continued tightening of the locking knob  110  compresses the deformable region of the hollow member  104 , thereby placing pressure against the measurement member  102  at the approximate point of the deformable region. Once the deformable region of the hollow member  104  is sufficiently compressed by the locking knob  110 , the measurement member  102  is fixed in place within the hollow member  104 . In one embodiment, the deformable region is formed by forming a plurality of slits along the circumference of the hollow member  104  at the approximate location of the deformable region.  
      Turning to  FIG. 3 , a device  100  of the present invention is shown that includes a light component  126  secured to the hollow member  104 . The light component  126  is capable of being oriented to direct light toward the distal end of the hollow member  104 . In operation, the light component  126  provides illumination within the body in order to facilitate the placement of the device  100  within the body. Also, in embodiments of the device  100  where the flange  106  includes a plurality of measurement marks  122 , the light component  126  is capable of being oriented to also direct light toward the flange  106 , thereby increasing the visibility of the measurement marks  122  on the flange  106  when the device  100  is within the body. As illustrated, the light component  126  includes attachment means  128  used to secure the light component  126  to the hollow member  104 . In one embodiment, the attachment means  128  are removable from the hollow member  104 . The attachment means  128  may be, for example screws designed for secure insertion into corresponding openings on the hollow member  104 , or snap-on clips. When the light component  126  uses snap-on clips as the attachment means  128 , the light component  126  may be positioned at various locations along the length of the hollow member  104  and at various positions around the circumference of the hollow member  104 . In another embodiment, the light component  126  is an integral part of the hollow member  104 . Here, the light component  126  is permanently affixed to the hollow member  104  in a predetermined orientation, such as, e.g., an orientation that directs light substantially toward the distal end of the hollow member  104  and to flange  106 , and is not removable from the hollow member  104 .  
      In one embodiment of light component  126 , light component  126  is powered using a battery that is disposed within the interior of light component  126 . In another embodiment, an external power source is provided in lieu of a battery integrated into the interior of the light component  126 . When an external power source is used, lead wires are provided that electrically couple the light component to the external power source. The lead wires preferably include a positive wire, a negative wire, and a ground wire. Alternatively, the lead wires include a positive wire and a negative wire, with one of the wires being grounded at some location outside the body, such as, e.g., near the external power source.  
       FIG. 4  is a device  200  of the present invention that incorporates a light element  230  as part of the measurement member  202 . The device  200  includes a hollow member  204  and a measurement member  202  configured to slide coaxially within the hollow member  204 . Measurement member  202  includes a measurement scale  218  on its proximal portion that is substantially the same as measurement scale  118  of device  100 . Similarly, device  200  includes a locking mechanism  224  that is substantially the same as locking mechanism  124  of device  100 . For example, as with locking mechanism  124 , locking mechanism  224  preferably includes a collar  208  disposed around the circumference of the hollow member  204  and a locking knob  210  insertable into the collar  208 . Further, flange  206  of device  200  is substantially the same as flange  106  of device  100  and is located at the distal end of hollow member  204 .  
      Measurement member  202  of device  200  includes a lumen  216 . Additionally, device  200  includes a light element  230  disposed within lumen  216 . As illustrated, the light element  230  is located in the lumen  216  in the distal portion of the measurement member  202 . In a preferred embodiment, the light element  230  is located at the distal end of the measurement member  202 . Light element  230  is a light-emitting component capable of generating light that is directed substantially in a distal direction when the device  200  is placed within the body. Light element  230  may be any suitable light source, such as, e.g., a light-emitting diode, a laser, an incandescent light bulb, a fluorescent substance, or the like. In another embodiment, the light element  230  is an array of individual light-emitting components rather than a single light-emitting component. When an array of individual light emitting components are used instead of a single light emitting component, the light element  230  is capable of continually emitting light in the event one of the array of light emitting components fails during the operation of device  200 .  
      To allow for light to pass there through, measurement member  202  is preferably manufactured of a substantially transparent or translucent material such as plastic. In one embodiment, the entire measurement member  202  is constructed from a substantially transparent or translucent material. In another embodiment, the distal portion of the measurement member  202  is constructed from a substantially transparent or translucent material while the remaining portion of the member  202  is constructed from a substantially opaque material such as a metallic substance.  
      A set of leads  232   a  and  232   b  electrically couple the light element  230  to a power source  214 . In a preferred embodiment, one of the leads is a positive electrical wire while the other lead is a negative electrical wire. In one embodiment, the leads  232   a ,  232   b  are disposed within the lumen  230  of the measurement member  202 . The power source  214  is a component that is capable of providing power to the light element  230 , such as, e.g., a battery or the like. As illustrated in  FIG. 4 , the power source  214  is preferably located at the proximal end of the measurement member  202  and, specifically, housed within a handle  212 . The handle.  212  is preferably positioned at the proximal end of measurement member  202 . The handle  212  has an internal space  222  designed to house the power source  214 . The internal space  222  is preferably water tight to prevent damage to the power source  214 , a switch  216 , or other components that may be disposed therein.  
      The handle  212  also includes a switch  216  electrically coupled to the power source  214  that enables a user to control the power supplied to the light element  230 , as desired. In one embodiment, the switch  216  enables a user to either turn on or turn off the supply of power to the light element  230 . Alternatively, the switch enables a user to vary the amount of power supplied to the light element  230 , thereby allowing a user to variably dim the light element  230  rather than merely turning it on or off. In the illustrated embodiment, the switch  216  is a toggle or flip switch that may be alternated between a first position and a second position. The first and second positions generally correspond to on and off positions respectively. In another embodiment, the switch  216  is positioned at the proximal end of the handle  212 , and is operated by turning the switch  216  in a circular fashion. Alternatively, the switch  216  is a membrane component positioned at the proximal end of the handle  212 , and is operated by depressing the membrane.  
      In an alternative embodiment of device  200 , measurement member  202  does not include a lumen  216  but, rather, is a solid member formed of a transparent or translucent material such as plastic. In this embodiment, the material that is used to form measurement member  202  encases both light element  230  and leads  232   a ,  232   b . This is in comparison to the embodiment of device  200  illustrated in  FIG. 4  wherein light element  230  and leads  232   a  and  232   b  are positioned within a lumen  216 . When the device  200  includes a solid measurement member  202  encasing light element  230  and leads  232   a ,  232   b , movement of either light element  230  or leads  232   a ,  232   b  within the member  202  is substantially restricted. This embodiment of measurement member  202  may be manufactured by coextruding, from a plastic material, both measurement member  202  and leads  232   a ,  232   b , thereby manufacturing a member  202  with built-in leads  232   a ,  232   b . With the embodiment illustrated in  FIG. 4 , by comparison, leads  232   a  and  232   b  lie freely within lumen  216 .  
      In another embodiment of device  200 , hollow member  204  is composed of a substantially transparent or translucent material. When constructed of substantially transparent or translucent material, hollow member  204  enables light emitted from the light element  230  to also be emitted there through. As a result, this embodiment of device  200  enables light element  230  to emit a greater percentage of light to the areas surrounding device  200 .  
      Device  200 , in another embodiment, includes a plurality of ports on the distal portion of hollow member  204 , such as ports  326  shown in  FIG. 5  and to be discussed herein. The ports allow an amount of light to be emitted through the hollow member  204  even when the hollow member  204  is not constructed of a translucent material. For example, a hollow member  204  manufactured from a metallic material or an opaque plastic material will still allow some amount of light to shine there through and onto the areas surrounding the device  200  when hollow member  204  includes a plurality of ports on its distal portion.  
      Illustrated in  FIG. 5  is a device  300  of the present invention. Device  300  includes a hollow member  304  and a measurement member  302  configured to slide coaxially within the hollow member  304 . Flange  306 , located at the distal end of the hollow member  304 , is substantially the same as flange  106  of device  100 . Measurement member  302  is substantially similar to measurement member  202  of device  300 . For example, measurement member  302  includes a measurement scale  318  along its proximal region.  
      Also, measurement member  302  includes a light element  330  disposed in the distal portion of measurement member  302  and leads  332   a ,  332   b  electrically coupled to the light element  330 . In a preferred embodiment, light element  330  is located at the distal end of measurement member  302 . Also, light element  330  is a light-emitting component capable of generating light, such as, e.g., a light-emitting diode, a laser, an incandescent light bulb, a fluorescent material, or the like, and may be either a single light-emitting component or an array of light-emitting components.  
      In one embodiment of measurement member  302 , member  302  has a lumen  316  in which light element  330  and leads  332   a ,  332   b  are disposed. In another embodiment, measurement member  302  has no lumen, but is solid and manufactured from a substantially transparent or translucent material, such as, e.g., plastic. Here, measurement member  302  encases light element  330  and leads  332   a ,  332   b , reducing the degree of movement of leads  332   a ,  332   b , as compared to the measurement member  302  having a lumen  316  and leads  332   a ,  332   b  lying freely within lumen  316 . For example, this embodiment of measurement member  302  may be manufactured by being coextruded from a plastic material, and having built-in leads  332   a ,  332   b.    
      The leads  332   a ,  332   b  are preferably a positive electrical wire and a negative electrical wire. Further, the leads  332   a ,  332   b  electrically couple light element  330  to a power source  314 , with may be, e.g., a battery or the like. As with device  200 , the power source  314  of device  300  is preferably located at the proximal end of the measurement member  302  and, specifically, housed within a handle  312 . The handle  312  is preferably positioned at the proximal end of measurement member  302 . The power source is housed within an internal space  322  of handle  312 . A switch  316  on the handle  312  and electrically coupled to power source  314  enables a user to turn on or off the power supplied to light element  330 . Alternatively, switch  316  allows a user to vary the level of power supplied to light element  330  rather than merely providing an on or an off setting.  
      Device  300  includes a locking mechanism  324  that includes a locking knob  310  insertable into a collar  308 . The collar  308  is disposed between fixed stops  328   a  and  328   b . Fixed stop  328   a  is located adjacent to the distal end of collar  308 , whereas fixed stop  328   b  is located adjacent to the proximal end of collar  308 . Fixed stops  328   a  and  328  b maintain collar  308  at a fixed position along the length of hollow member  304 , i.e., the fixed stops  328   a  and  328   b  prevent the collar  308  from moving along the length of hollow member  304 . Although collar  308  is fixed in place along the length of hollow member  304  by fixed stops  328   a ,  328   b , the collar  308  is still rotatable around the circumference of hollow member  304 . As a result of the rotating aspect of collar  308 , manipulation and operation of locking mechanism  324  is facilitated since a user is able to rotate collar  308  to a suitable position while operating device  300 . Other than the rotating aspect of locking mechanism  324 , locking mechanism  324  operates in substantially the same manner as locking mechanism  124  of device  100 . For example, in one embodiment, hollow member  304  includes an opening that is configured for the insertion of the locking knob  310  there through. Further, collar  308  also includes an opening that is capable of being aligned with that opening of the hollow member  304 . Therefore, when a user desires to lock the position of measurement member  302  within hollow member  304 , the user tightens locking knob  310 , while knob  310  is inserted into collar  308  and while the openings of collar  308  and hollow member  304  are aligned. The user continues tightening locking knob  310  until locking knob  310  engages and contacts measurement member  302 . As a result, locking knob  310  places pressure on measurement member  302 , thereby substantially preventing proximal or distal movement of the measurement member  302  within hollow member  304 . As with locking mechanism  124 , another embodiment of locking mechanism  324  operates by compressing a deformable region on the hollow member  304  located substantially where collar  308  is placed on the circumference of the hollow member  304 . Here, continued tightening of locking knob  310  exerts pressure on the deformable region, thereby compressing that region and also placing pressure on measurement member  302 .  
      As previously mentioned, device  300  includes a light element  330  that is either disposed within a lumen  316  of measurement member  302  or encased by measurement member  302  when member  302  does not include a lumen  316 . The measurement member  302  is constructed, in whole or in part, of a transparent or translucent material in order to allow light emitted from the light element  330  to pass there through. In one embodiment, the entire measurement member  302  is constructed from a substantially transparent or translucent material. In another embodiment, the distal portion of the measurement member  302  is constructed from a substantially transparent or translucent material while the remaining portion of the member  302  is constructed from a substantially opaque material such as a metallic substance.  
      In the illustrated embodiment, device  300  includes a plurality of ports  326  located on the distal portion of hollow member  304 . Ports  326  allow an amount of light to be emitted through hollow member  304  even when hollow member  304  is manufactured from an opaque material, such as, e.g., a metallic substance. When hollow member  304  is manufactured from a metallic material or an opaque plastic material, light emitting from light element  330  will pass through both the measurement member  302 , at the transparent or translucent portions of member  302 , and through ports  326  of hollow member  304 . As a result, ports  326  increase the area surrounding device  300  that is illuminated by light element  330 , particularly when hollow member  304  is composed of an opaque material. In an alternative embodiment, the entire body of hollow member  304  is manufactured from a transparent or translucent material, thereby allowing light emitting from light element  330  to pass through substantially the entire length of hollow member  304 .  
      All of the devices of the present invention include alternative embodiments where the position of the measurement member within the hollow member, after determining the length of the bodily part being measured, is capable of being fixed without the use of locking mechanisms  124 ,  224 , or  324 . Rather than requiring a separate locking mechanism component  124 ,  224 , or  324 , these alternative embodiments of the devices of the present invention include hollow members and measurement members designed to self-lock, i.e., without requiring the separate locking mechanisms of devices  100 ,  200 , or  300 . Several devices having self-locking hollow members and measurement members are illustrated in cross-section in  FIGS. 6   a - f . The devices in  FIGS. 6   a - f  incorporate hollow members and measurement members incorporating self-locking features that, first, allow for the measurement member to travel longitudinally within the hollow member while also restricting the rotation of the measurement member within the hollow member. Second, the self-locking features of these devices allow for a user to fix the position of the measurement member within the hollow member after a measurement of a body part has been taken.  
      With the exception of the specifically discussed features, the devices illustrated in  FIGS. 6   a - f  are substantially similar to devices  100 ,  200 , and  300 . For example, the devices illustrated in  FIGS. 6   a - f  all include an elongated measurement member insertable into an elongated hollow member and capable of being advanced coaxially within the hollow member. A flange is present on the distal end of the hollow member and is operable to stop the progression of the hollow member within a body while enabling continued progression of the measurement member. The measurement member includes a measuring scale located on a proximal portion of the member, in addition to a handle attached to the proximal end of the measurement member. Further, the devices illustrated in  FIGS. 6   a - f  may incorporate any of the light emitting components discussed herein. Unlike devices  100 ,  200 , and  300 , however, the devices in  FIGS. 6   a - d  do not include a separate locking mechanism but, rather, include the integrated self-locking features described herein.  
      Referring to  FIGS. 6   a ( i ) and  6   a ( ii ), one embodiment of a self-locking device of the present invention, device  400 ( a ), is illustrated. As previously discussed, with the exception of a separate locking mechanism, device  400 ( a ) includes substantially the same components as the other devices of the present invention, such as device  200  and  300 , and is operated in substantially the same manner to obtain a measurement of a dimension of a body part. Device  400 ( a ) includes a hollow member  404 ( a ) and a measurement member  402 ( a ). Hollow member  404 ( a ) and measurement member  402 ( a ) are substantially similar to hollow member  104  and measurement member  102 , with the exception of the shapes of hollow member  404 ( a ) and measurement member  402 ( a ). Hollow member  404 ( a ) and measurement member  402 ( a ) are oval in cross-section. Further, measurement member  402 ( a ) is slightly flatter in cross-section that hollow member  404 ( a ), i.e., has a shorter minor axis  419  than the minor axis  421  of hollow member  404 ( a ). As with the other embodiments of the devices of the present invention, measurement member  402 ( a ) is still capable of being placed within hollow member  404 ( a ) and manipulated coaxially within hollow member  404 ( a ). As seen in  FIG. 6   a ( i ), when a user desires to progress measurement member  402 ( a ) within hollow member  404 ( a ), device  400 ( a ) is operated so that measurement member  402 ( a ) is capable of being progressed coaxially within hollow member  404 ( a ). For example, to enable to move measurement member  402 ( a ) either distally or proximally within hollow member  404 ( a ), device  400 ( a ) is operated so that the major axis  403  of measurement member  402 ( a ) is substantially parallel to the major axis  405  of hollow member  404 ( a ). When the major axes  403 ,  405  are substantially parallel, measurement member  402 ( a ) may be advanced within hollow member  404 ( a ).  
      Due to the relative cross-sectional shapes of the members, however, the ability to rotate measurement member  402 ( a ) while traveling within hollow member  404 ( a ) is restricted. The restriction of the rotation of measurement member  402 ( a ) increases the ability to determine the position of the proximal end of hollow member  404 ( a ) along the measurement scale of measurement member  402 ( a ). Further, the position of measurement member  402 ( a ) within hollow member  404 ( a ) is capable of being fixed by forcibly rotating measurement member  402 ( a ) while a portion of member  402 ( a ) is still within hollow member  404 ( a ). For example, to fix the position of measurement member  402 ( a ) relative to hollow member  404 ( a ), a user will forcibly rotate measurement member  402 ( a ) so that major axes  403 ,  405  are no longer in a parallel relationship. As a result, measurement member  402 ( a ) will come into contact with the internal walls of hollow member  404 ( a ) at at least two points along the internal walls of hollow member  404 ( a ). The user then proceeds to exert sufficient force to fix the position of measurement member  402 ( a ) within hollow member  404 ( a ). Therefore, unlike devices  100 ,  200 , and  300 , a separate locking mechanism is not required to fix the position of measurement member  402 ( a ) within hollow member  404 ( a ). Alternative embodiments of device  400 ( a ) are capable of utilizing different cross-section shaped measurement members  402 ( a ) and hollow member  404 ( a ) but having major axes  403 ,  405  that, when in substantial parallel relationship, enable measurement member  402 ( a ) to be manipulated within hollow member  404 ( a ) and, when displaced from a substantial parallel relationship, result in the fixation of measurement member  402 ( a ) within hollow member  404 ( a ).  
      Referring to  FIG. 6b , another embodiment of a self-locking device of the present invention, device  400 ( b ), is illustrated. Device  400 ( b ) includes a hollow member  404 ( b ) having a slot  413  defined by side walls  413   a  and a measurement member  402 ( b ) having a protrusion  415 . With the exception of a separate locking mechanism, device  400 ( b ) includes substantially the same components as the other devices of the present invention, such as device  200  and  300 , and is operated in substantially the same manner to obtain a measurement of a dimension of a body part. As with the other devices of the present invention, measurement member  402 ( b ), during operation of device  400 ( b ), is placed within, and in coaxial alignment with, hollow member  404 ( b ) to allow measurement member  402 ( b ) to be manipulated proximally and distally within hollow member  404 ( b ). Slot  413 , in a preferred embodiment, extends length wise, and for substantially the entire length, of hollow member  404 ( b ). In another embodiment, slot  413  extends longitudinally along the distal portion of hollow member  404 ( b ) for at least a length that is substantially equivalent to the length of the measurement scale on the proximal portion of the measurement member  402 ( b ). Protrusion  415  of measurement member  402 ( b ), in one embodiment, is a single protrusion located at one position on measurement member  402 ( b ). In another embodiment, protrusion  415  is a protrusion that extends length wise along substantially the entire length of measurement member  402 ( b ). In the embodiment where slot  413  extends longitudinally along the distal portion of hollow member  404 ( b ) for at least a length that is substantially equal to the length of the measurement scale, protrusion  415  is preferably a single protrusion located on the distal portion of measurement member  402 ( b ).  
      While manipulating measurement member  402 ( b ) within hollow member  404 ( b ), protrusion  415  is oriented so that it lies within slot  413 . The positioning of protrusion  415  within slot  413  prevents undesired rotation of measurement member  402 ( b ) within hollow member  404 ( b ) while a body part is being measured. After measuring a bodily part using measurement member  402 ( b ), the position of member  402 ( b ) within hollow member  404 ( b ) is capable of being fixed by rotating measurement member  402 ( b ) in order to forcibly engage protrusion  415  against a side wall  413   a  of slot  413 . This is accomplished by, for example, continuing to rotate measurement member  402 ( b ) until protrusion  415  physically contacts a side wall  413   a  and then continuing to apply rotational pressure in that direction in order to force at least a portion of protrusion  415  beyond slot  413 , i.e., at least a portion of protrusion  415  is forced under a side wall  413   a . Consequently, the position of measurement member  402 ( b ) becomes fixed within hollow member  404 ( b ) without requiring a separate locking mechanism.  
       FIG. 6   c  illustrates another embodiment of a self-locking device of the present invention, device  400 ( c ). Device  400 ( c ) includes a hollow member  404 ( c ) and a measurement member  402 ( c ). Hollow member  404 ( c ) includes an opening  417  through which a fastening member  407  may be inserted. As with the other fastening members of the other devices discussed herein, fastening member  407  may be, e.g., a screw. Measurement member  402 ( c ) includes a flat face  409  that preferably extends the length of the member  402 ( c ). In another embodiment, flat face  409  extends longitudinally along the distal portion of measurement member  402 ( c ) for at least a length that is substantially equivalent to the length of the measurement scale on the proximal portion of the measurement member  402 ( c ). With this embodiment, the opening  417  and the fastening member  407  are disposed on the distal portion of the hollow member  404 ( c ).  
      Like the other devices of the present invention, measurement member  402 ( c ), during operation of device  400 ( c ), is placed within, and in coaxial alignment with, hollow member  404 ( c ). Measurement member  402 ( c ) is then manipulated proximally or distally within hollow member  404 ( c ) in order to determine the length of the body part being measured by observing the location of the proximal end of hollow member  404 ( c ) along a measurement scale on the proximal portion of measurement member  402 ( c ). With the exception of a separate locking mechanism, device  400 ( c ) includes substantially the same components as the other devices of the present invention, such as device  200  and  300 , as is operated in substantially the same manner to obtain a measurement of a dimension of a body part.  
      During operation, fastening member  407  is inserted into opening  417  of hollow member  404 ( c ). While a measurement is being taken, the position of fastening member  407  within opening  417  restricts the ability to rotate measurement member  402 ( c ) within hollow member  404 ( c ). After a measurement is taken, the position of measurement member  402 ( c ) within hollow member  404 ( c ) is fixed by further tightening fastening member  407  until it contacts the flat face  409  of measurement member  402 ( c ). To facilitate this process, it may be necessary to orient measurement member  402 ( c ) in order for flat face  409  to align with opening  417  of hollow member  404 ( c ). Once fastening member  407  contacts the flat face  409 , additional tightening of fastening member  407  exerts pressure upon measurement member  402 ( c ), thereby fixing measurement member  402 ( c ) at that position within hollow member  404 ( c ). As a result, device  400 ( c ) enables a user to fix the measurement member  402 ( c ) at a given position within hollow member  404 ( c ) without requiring the use of a separate locking mechanism, as compared to device  100 ,  200 , and  300 .  
      Referring now to  FIG. 6d , another embodiment of a self-locking device of the present invention is shown. Device  400 ( d ) includes a measurement member  402 ( d ) suitable for insertion within a hollow member  404 ( d ). Like measurement member  402 ( c ) of device  400 ( c ), measurement member  402 ( d ) includes a flat face  409  that preferably extends substantially the length of the member  402 ( d ). Hollow member  404 ( d ) includes, on its internal surface, a ridge  411 . In one embodiment, ridge  411  extends substantially the entire length of hollow member  404 ( d ). In another embodiment, ridge  411  is a single dimple or protuberance at one location on the internal surface of hollow member  404 ( d ). In another embodiment of device  400 ( c ), flat face  409  extends longitudinally along the distal portion of measurement member  402 ( d ) for at least a length that is substantially equivalent to the length of the measurement scale on the proximal portion of member  402 ( d ). With this embodiment, ridge  411  is a single protuberance disposed at one location on the internal surface of the distal portion of hollow member  404 ( d ).  
      Device  400 ( c ) includes substantially the same components as devices  200  and  300 , with the exception of the locking mechanisms of those devices, i.e., device  400 ( c ) does not require a separate locking mechanism. Device  400 ( d ) is also operated in substantially the same manner of the other devices of the present invention in order to determine a dimension of a body part.  
      With device  400 ( d ), however, measurement member  402 ( d ), while a dimension of a body part is being determined, is preferably oriented within hollow member  404 ( d ) such that flat face  409  is oriented toward ridge  411 . In this manner, measurement member  402 ( d ) is freely slidable coaxially or longitudinally within hollow member  404 ( d ). Additionally, the range of rotational movement of measurement member  402 ( d ) within hollow member  404 ( d ) is limited by the combination of ridge  411  and flat face  409 , i.e., ridge  411  restricts the rotation of measurement member  402 ( d ) when ridge  411  contacts an edge of flat face  409 .  
      To fix the position of measurement member  402 ( d ) within hollow member  404 ( d ), after determining the dimension of a body part, such as the length of the cervix, the measurement member  402 ( d ) is rotated so that one edge of flat face  409  contacts ridge  411 . Sufficient additional rotational force is then applied to measurement member  402 ( d ) so that flat face  409 , and therefore measurement member  402 ( d ), is maintained in a fixed position by ridge  411 . As a result, the incorporation of a ridge  411  on the internal surface of hollow member  404 ( d ) and a flat surface  409  on measurement member  402 ( d ) allows a user to fix the position of measurement member  402 ( d ) within hollow member  404 ( d ), thereby preserving the location of the proximal end of hollow member  404 ( d ) along a measuring scale on the proximal portion of measurement member  402 ( d ), i.e., a measurement of a dimension of a body part, without the use of a separate locking mechanism.  
      Turning to  FIG. 6e , another embodiment of a self-locking device of the present invention is shown. Device  400 ( e ) includes a measurement member  402 ( e ) suitable for insertion within a hollow member  404 ( e ). Measurement member  402 ( e ) includes an indentation  420  that extends longitudinally along the length of measurement member  402 ( e ). Indentation  420  preferably extends substantially the length of measurement member  402 ( e ). Hollow member  404 ( e ) includes an opening  417  through which a fastening member  407  may be inserted. Device  400 ( e ) includes substantially the same components as devices  200  and  300 , with the exception of the locking mechanisms of those devices, i.e., device  400 ( e ) does not require a separate locking mechanism. Device  400 ( e ) is also operated in substantially the same manner of the other devices of the present invention in order to determine a dimension of a body part.  
      With device  400 ( e ), however, measurement member  402 ( e ), while a dimension of a body part is being determined, is preferably oriented within hollow member  404 ( e ) such that fastening member  407 , which is inserted into opening  417  during operation, extends into indentation  420 . As a result, measurement member  402 ( e ) is freely slidable coaxially or longitudinally within hollow member  404 ( e ). Further, the range of rotational movement of measurement member  402 ( e ) within hollow member  404 ( e ) is limited by the extension of fastening member  407  within indentation  420 .  
      To fix the position of measurement member  402 ( e ) within hollow member  404 ( e ), after determining the dimension of a body part, such as the length of the cervix, fastening member  407  is tightened such that it engages the bottom surface of indentation  420 . Subsequently, fastening member  407  is additionally tightened to ensure that measurement member  402 ( e ) is maintained in a fixed position by the engagement of the bottom surface of indentation  420  by fastening member  407 . As a result, the incorporation of an indentation  420  on measurement member  402 ( e ), in combination with a fastening member  407  insertable into hollow member  404 ( e ) and capable of being engaged with indentation  420 , allows a user to fix the position of measurement member  402 ( e ) within hollow member  404 ( e ), thereby preserving the location of the proximal end of hollow member  404 ( e ) along a measuring scale on the proximal portion of measurement member  402 ( e ), i.e., a measurement of a dimension of a body part, without the use of a separate locking mechanism.  
      Referring now to  FIG. 6   f , another embodiment of a self-locking device of the present invention is shown. Device  400 ( f ) includes a measurement member  402 ( f ) suitable for insertion within a hollow member  404 ( f ). Like measurement member  402 ( e ) of device  400 ( e ), measurement member  402 ( f ) includes an indentation  422  that preferably extends longitudinally along substantially the length of the member  402 ( f ). Hollow member  404 ( f ) includes, on its internal surface, a protrusion  424 . In one embodiment, protrusion  424  extends substantially the entire length of hollow member  404 ( f ). In another embodiment, protrusion  424  is a single dimple or detent at one location on the internal surface of hollow member  404 ( f ). Device  400 ( f ) includes substantially the same components as devices  200  and  300 , with the exception of the locking mechanisms of those devices, i.e., device  400 ( f ) does not require a separate locking mechanism. Device  400 ( f ) is also operated in substantially the same manner of the other devices of the present invention in order to determine a dimension of a body part.  
      With device  400 ( f ), however, measurement member  402 ( f ), while a dimension of a body part is being determined, is preferably oriented within hollow member  404 ( f ) such that protrusion  424  lies within indentation  422 . In this manner, measurement member  402 ( f ) is freely slidable coaxially or longitudinally within hollow member  404 ( f ). Additionally, the range of rotational movement of measurement member  402 ( f ) within hollow member  404 ( f ) is limited by the positioning of protrusion  424  within indentation  422 .  
      To fix the position of measurement member  402 ( f ) within hollow member  404 ( f ), after determining the dimension of a body part, such as the length of the cervix, the measurement member  402 ( f ) is rotated so that one edge of indentation  422  contacts protrusion  424 . Sufficient additional rotational force is then applied to measurement member  402 ( f ) so that indentation  422 , and therefore measurement member  402 ( f ), is maintained in a fixed position by protrusion  424 . As a result, the incorporation of a protrusion  424  on the internal surface of hollow member  404 ( f ) and an indentation on measurement member  402 ( f ) allows a user to fix the position of measurement member  402 ( f ) within hollow member  404 ( f ), thereby preserving the location of the proximal end of hollow member  404 ( f ) along a measuring scale on the proximal portion of measurement member  402 ( f ), i.e., a measurement of a dimension of a body part, without the use of a separate locking mechanism.  
      Turning to FIGS.  6 ( g )( i ) and  6 ( g )( ii ), another embodiment of a self-locking device of the present invention, device  500 , is shown.  FIG. 6 ( g )( ii ) is a cross-sectional view of device  500  along the line  6 ( g )( ii ). Device  500  includes a hollow member  504  and a measurement member  502 . A flange  506  is located at the distal end of hollow member  504  and allows for measurement member  502  to slide there through. Hollow member  504  includes an opening  517  through which a fastening member  507  may be inserted. As with the other fastening members of the other devices discussed herein, fastening member  507  may be, e.g., a screw. Further, fastening member  507 , in one embodiment of device  500 , is permanently fixed in position within opening  517  and hollow member.  504 . Measurement member  502  includes a first and second flat face  509   a ,  509   b  that are in opposing relation to each other. The embodiment of device  500  illustrated in  FIG. 6   g ( i )includes flat faces  509   a ,  509   b  that extend longitudinally along the distal portion of measurement member  502  for at least a length that is substantially equivalent to the length of a measurement scale  518  on the proximal portion of the measurement member  502 . Here, the opening  517  and the fastening member  507  are disposed on the distal portion of the hollow member  504 .  
      Like the other devices of the present invention, measurement member  502 , during operation of device  500 , is placed within, and in coaxial alignment with, hollow member  504 . Measurement member  502  is then manipulated proximally or distally within hollow member  504  in order to determine the length of the body part being measured by observing the location of the proximal end of hollow member  504  along a measurement scale on the proximal portion of measurement member  502 . With the exception of a separate locking mechanism, device  500  includes substantially the same components as the other devices of the present invention, such as device  200  and  300 . In the embodiment of device  500  shown in FIGS.  6 ( g )( i ) and  6 ( g )( ii ), the device  500  includes a handle  512  attached to the proximal end of the measurement member  502  that houses a power source  514  and a switch  516  that controls the application of power from the source  514  to a light element  530 . The light element  530  is preferably located within the distal portion of measurement member  502  and is electrically coupled to the power source  514  via lead wires  532   a  and  532   b . Lead wires  532   a  and  532   b  also electrically couple the power source  514  to the switch  516 . When a light element  530  is provided, the measurement member  502  and the hollow member  504  are manufactured from a substantially translucent material such as plastic. Alternatively, device  500  is provided without light element  530 , power source  514 , switch  516 , and lead wires  532   a ,  532   b  in order to reduce manufacturing costs of the device  500 .  
      Device  500  is operated in substantially the same manner as, e.g., devices  200  and  300  to obtain a measurement of a dimension of a body part. During operation, fastening member  507  is disposed within opening  517  of hollow member  504 . Preferably, measurement member  502  is oriented within hollow member  504  such that one of flat faces  509   a  or  509   b  is positioned toward the fastening member  507 . In one embodiment, corresponding markings are provided on the proximal portions of both measurement member  502  and hollow member  504  that, when in alignment, indicate to the user that measurement member  502  is oriented such that one of flat faces  509   a  or  509   b  is positioned toward fastening member  507 .  
      While a measurement is being taken, the position of fastening member  507  within opening  517  restricts the ability to rotate measurement member  502  within hollow member  504 . For the embodiment of device  500  where the fastening member  507  is fixed in position within opening  517 , after a measurement is taken, the position of measurement member  502  within hollow member  504  is fixed by forcibly rotating the measurement member  502  until one of the ends  510 , i.e., not flat face  509   a  or  509   b , faces fastening member  507 . When this is achieved, measurement member  502  is held in place within hollow member  504  by pressure exerted by fastening member  507  on one of the ends of measurement member  502 . Alternatively, in an embodiment of device  500  where fastening member  507  is not permanently fixed but, rather, is removable from opening  517 , to fix the position of measurement member  502  a user may further tighten fastening member  507  until it contacts a flat face  509   a  or  509   b  of measurement member  502 . Once fastening member  507  contacts a flat face  509   a  or  509   b , additional tightening of fastening member  507  exerts pressure upon measurement member  502 , thereby fixing measurement member  502  at that position within hollow member  504  ). As a result, device  500  enables a user to fix the measurement member  502  at a given position within hollow member  504  without requiring the use of a separate locking mechanism, as compared to devices  100 ,  200 , and  300 .  
      In another embodiment of the present invention, any of the devices disclosed herein is modified by the addition of a spring-loaded outer sleeve  700  to the handle of that device. The spring-loaded outer sleeve  700  of the present invention, when used in conjunction with one of the devices disclosed herein, allows a constant pressure to be maintained on the device, and specifically on the measurement member, while the device is being advanced within the body. The outer sleeve  700  also prevents undue pressure from being exerted against a bodily surface during the operation of the device by absorbing some of the pressure used to manipulate the device within the body. As a result, outer sleeve  700  reduces the risk of the device puncturing a bodily wall while a measurement of a dimension of a body part is taken with the device.  
      As illustrated in  FIG. 7 , outer sleeve  700  includes an outer shell  704  capable of being placed over a handle of a device of the present invention. As shown in Figure  7 , outer sleeve  700 , and specifically outer shell  704 , is placed over handle  212  of device  200 . Outer sleeve  700  is, however, capable of being placed over any of the other handles of the other devices disclosed herein. Outer shell  704  includes sufficient interior space to accommodate a handle of a device of the present invention as well as a spring element  702 , or other resilient structure. In a preferred embodiment, spring element  702  is secured to a proximal wall of the outer shell  704  using a suitable attachment means, such as, e.g., an adhesive.  
      Preferably, outer shell  704  is placed over, for example, handle  212  of device  200 , and handle  212  is situated distally relative to spring element  702 . A user will then advance measurement member  202  by manipulating outer sleeve  700 . As measurement member  202  is advanced, spring element  702  absorbs any force over a preset level, the level being dependent on the resiliency of the spring element  702  incorporated into outer sleeve  700 . Therefore, outer sleeve  700  prevents the force used to advance measurement member  202  from exceeding a present level. Additionally, after the distal end of measurement member  202  contacts a body wall or surface, outer sleeve  700  prevents measurement member  202  from puncturing that surface by absorbing additional force via spring element  702 .  
      In one embodiment, outer sleeve  700  is manufactured from a metallic material, such as, e.g., brass, stainless steel, or the like. In another embodiment, outer sleeve  700  is manufactured from a plastic material. When formed from plastic, outer sleeve  700  may be manufactured using a plastic extrusion technique known in the art. Preferably, the outer sleeve  700  is placed on a handle of a device of the present invention, such as handle  212 , at the time the entire device is manufactured and assembled. In one embodiment, the handle is placed into the outer shell  704  and distal relative to the spring element  702 . The distal end of the outer shell  704  is then crimped in order to fix the outer sleeve  700  around the handle. In another embodiment, the handle is placed within the outer shell  704  and then a suitable element, such as, e.g., a washer or the like, is affixed over the distal opening of the outer shell  704  using a suitable adhesive or soldering technique in order to maintain the handle within the outer sleeve  700 . Alternatively, the outer surface of the handle and the inner surface of the outer shell  704  of the sleeve  700  may contain corresponding threads or grooves, thereby enabling the sleeve  700  to be threaded onto the handle. The outer sleeve  700 , in another embodiment, is press fit onto the handle.  
      Illustrated in  FIG. 8  is another embodiment of the present invention, device  800 .  FIG. 8  is a top plan view of device  800 ,  FIG. 8C  is a side view of device  800 , and  FIG. 8D  is a side view of the measurement member  802  of device  800  in isolation. Further,  FIG. 8A  is a cross-sectional view of device  800  along the line  8 A- 8 A shown in  FIG. 8 , and  FIG. 8B  is a cross-sectional view of device  800  along the line  8 B- 8 B shown in  FIG. 8 . Device  800  includes a measurement member  802  and an outer member  804 . Measurement member  802  includes a measurement scale  818  that has a plurality of incremental markings. The incremental markings, in one embodiment of device  800 , extend for substantially the entire length of measurement member  802 . Outer member  804  includes an open side  805 , seen in  FIG. 8A , through which measurement member  802 , and therefore the measurement scale  818 , is visible while the measurement member  802  is disposed within the outer member  804 . The open side  805  also includes two extensions  807  that cover an edge of measurement member  802  while member  802  is disposed within outer member  804 . Extensions  807  secure measurement member  802  within outer member  804  while simultaneously allowing for movement of member  802  distally and proximally. Measurement member  802  also includes a flange  806  located on its distal end. The flange  806  is preferably a circular shape, a tear-drop shape, or another shape that does not exhibit sharp angles.  
      In operation, measurement member  802  is placed within and is slidably engaged by outer member  804 . Measurement member  802  is capable of being advanced distally and proximally while engaged by outer member  804 . In one exemplary use of device  800 , device  800  is used to measure the length of the cervix. When used to do so, the device  800  is placed within the vagina and advanced distally until the distal end of outer member  804  comes into contact with the cervical-uterine junction. Then, the measurement member  802  is advanced distally until flange  806  contacts the proximal surface of the cervix, thereby preventing further distal movement of the measurement member  802 . A user measures the length of the cervix by observing the location of the measurement scale  818  relative to the proximal end of the outer member  804 .  
      In one embodiment, the position of the measurement member  802  relative to the outer member  804  is maintained by friction between the members. For example, in this embodiment, measurement member  802  is manufactured to fit snugly within outer member  804 , but still allowing for movement distally and proximally while engaged within outer member  804 . The snug fit between the members enables the maintenance of the position of measurement member  802  within outer member  804  after a measurement is recorded.  
       FIG. 9  illustrates another embodiment of a device of the present invention, device  900 .  FIG. 9  is a top plan view of device  900 ,  FIG. 9C  is a side view of device  900 , and  FIG. 9D  is a side view of the measurement member  902  of device  900  in isolation.  FIG. 9A  is a cross-sectional view of device  900  along the line  9 A- 9 A shown in  FIG. 9 , and  FIG. 9B  is a cross-sectional view of device  900  along the line  9 B- 9 B shown in  FIG. 9 . Device  900  is similar to device  800  in that it includes a measurement member  902 , having a measurement scale  918  with a plurality of incremental markings, and an outer member  904 . Outer member  904  includes an open side  905 , seen in  FIG. 9A , through which measurement member  902  and measurement scale  918  is visible while measurement member  902  is disposed within outer member  904 . Measurement member  902  also includes a flange  906  located on its distal end that is preferably a circular shape, a tear-drop shape, or another shape that does not exhibit sharp angles. Device  900  is also operable in substantially the same manner as device  800 .  
      Rather than the extensions  807  of device  800  that maintain measurement member  802  within outer member  804 , the outer member  904  of device  900  interlocks with measurement member  902 . As seen in  FIGS. 9A and 9B , outer member  904  engages measurement member  902  without requiring extensions such as extensions  807  of device  800 . Here, measurement member  902  includes an angled body. Outer member  904  has angled space  903  configured to accept measurement member  902 . Due to the interlocking fit of outer member  904  and measurement member  902 , measurement member  902  is capable of being manipulated proximally and distally while disposed within angled space  903  of outer member  904 . Also, the interlocking fit of the members allows for measurement member  902  to be slidably engaged by outer member  904 . During manufacture of device  900 , outer member  904  may be crimped onto measurement member  902 .  
      With regard to materials of manufacture, the devices of the present invention are capable of being formed from either metallic materials or plastic materials. In one embodiment, the devices are manufactured from a metal, such as, e.g., brass, stainless steel, aluminum, or the like, using techniques known in the art. When the devices of the present invention are formed of a metallic material, the devices are capable of being sterilized in order to allow a device to be used repeatedly. Here, the devices are sterilized using an appropriate means, including, e.g., chemical sterilization, thermal sterilization, radiation, and the like, after use in order to allow to extend the lifetime of the device. In another embodiment, the devices of the present invention are formed from a plastic material. With these embodiments, the devices may be extruded from plastic using techniques known in the art. When plastic is used to manufacture the devices, the devices are disposable. Consequently, contamination issues are avoided by virtue of producing devices that are designed to be disposed after use, as compared to the embodiments formed with metal and requiring sterilization. The relative reduced cost of utilizing plastics to manufacture the devices, as opposed to metals, allows for the plastic embodiments of the devices to be intended as disposable units.  
      The present invention also provides various methods using the devices. For example, the invention provides a method for predicting the risk of preterm labor in an individual by performing the following steps. First, a device that includes a measurement member having a distal region and a proximal region, a hollow member through which the measurement member is inserted and advanced, and a flange engaged with the distal end of the hollow member, is inserted into the vagina. The flange of the device has a surface adapted to contact the cervix at the external uterine opening after the distal end of the hollow member is inserted into the vagina. The device is advanced within the vagina until the flange contacts the cervix at the external uterine opening. At this point, forward progress of the hollow member is prevented. The measurement member is continued to be advanced until the distal region of the measurement member contacts the cervical-uterine junction at the fornix vaginae. Subsequently, the length of the cervix in the fornix vaginae is determined by observing the position of the proximal end of the hollow member along a measurement scale located on the proximal portion of the measurement member. The length of the cervix in the fornix vaginae is inversely related to the risk of preterm labor.  
      As used herein the term “risk of preterm labor” refers to the risk that an individual will enter labor before the thirty-seventh week of gestation or pregnancy. Using the methods and devices of the present invention, in certain circumstances this risk can be predicted either when the individual is already pregnant or when the individual is not pregnant. When it is possible to evaluate the risk of preterm labor, a patient may gain valuable insight on what may occur during the pregnancy. Also as used herein the term “preterm delivery” is used interchangeably with preterm birth and refers to birth of the fetus as the result of preterm labor. Accordingly, it is contemplated that preterm delivery would occur as the result of preterm labor. Because babies born prematurely may have serious health problems, practitioners try to avoid preterm labor it at all possible. If vaginal bleeding occurs or if the fetal membranes rupture, preterm labor is difficult to stop. If, however, vaginal bleeding does not occur, and the membranes are not leaking amniotic fluid, bed rest with fluid given intravenously helps approximately one in two women. It should also be noted that if the cervix dilates beyond  5  centimeters, labor usually continues until the baby is born. Typically, magnesium sulfate given intravenously stops labor in a majority of cases. Using the devices and methods of the present invention will indicate whether such treatment may be needed in the future.  
      The invention also provides a method for predicting the risk of miscarriage in an individual. First, a device that includes a measurement member having a distal region and a proximal region, a hollow member through which the measurement member is inserted and advanced, and a flange engaged to the distal end of the hollow member, is inserted into the vagina. The flange of the device has a surface adapted to contact the cervix after the distal end of the hollow member is inserted into the vagina. The device is advanced within the vagina until the flange contacts the cervix, preferably at the external uterine opening. At this point, forward progress of the hollow member is prevented. The measurement member is continued to be advanced until the distal region of the measurement member contacts the cervical-uterine junction at the fornix vaginae. Subsequently, the length of the cervix in the fornix vaginae is determined by observing the position of the proximal end of the hollow member along a measurement scale located on the proximal portion of the measurement member. The length of the cervix in the fornix vaginae is inversely related to the risk of miscarriage.  
      The present invention also provides methods for predicting the ease of inducing labor. First, a device that includes a measurement member having a distal region and a proximal region, a hollow member through which the measurement member is inserted and advanced, and a flange engaged to the distal end of the hollow member, is inserted into the vagina. The flange of the device has a surface adapted to contact the cervix after the distal end of the hollow member is inserted into the vagina. The device is advanced within the vagina until the flange contacts the cervix, preferably at the external uterine opening. At this point, forward progress of the hollow member is prevented. The measurement member is continued to be advanced until the distal region of the measurement member contacts the cervical-uterine junction at the fornix vaginae. Subsequently, the length of the cervix in the fornix vaginae is determined by observing the position of the proximal end of the hollow member along a measurement scale located on the proximal portion of the measurement member. The length of the cervix in the fornix vaginae is inversely related to the ease of inducing labor.  
      The invention further provides a method for assessing the fertility of an individual. First, a device that includes a measurement member having a distal region and a proximal region, a hollow member through which the measurement member is inserted and advanced, and a flange engaged to the distal end of the hollow member, is inserted into the vagina. The flange of the device has a surface adapted to contact the cervix after the distal end of the hollow member is inserted into the vagina, includes a measurement scale, and is substantially translucent. Also, the flange is preferably off-set to the side of the hollow member to allow the flange to cover the external uterine opening while also allowing for the further advancement of the measurement member toward the fornix. The device is advanced within the vagina until the flange contacts the cervix, and preferably is placed against the external uterine opening. At this point, forward progress of the hollow member is prevented. The measurement member, however, is continued to be advanced toward the fornix until the distal region of the measurement member contacts the cervical-uterine junction at the fornix vaginae. Subsequently, the length of the cervix in the fornix vaginae is determined by observing the position of the proximal end of the hollow member along a measurement scale located on the proximal portion of the measurement member. Additionally, the dilation of the cervix is measured using the measurement scale on the flange. The length of the cervix in the fornix vaginae is inversely related to the fertility of an individual.  
      As used herein, the term “fertility” refers to the ability of a female to carry a fetus to the point where it is viable or can survive with the help of medical science, if necessary, when delivered, a female attempting pregnancy, preconceptional evaluation, or procedures involved with infertility treatment. Accordingly, fertility generally refers to the ability of a female to carry a fetus to a normal nine month term, as well as to any other shorter term where the infant would survive on its own or with critical care. By assessing the cervical length and diameter, a practitioner may achieve an appreciation of the fertility of the female, because a risk for preterm labor can be predicted. For example, if the practitioner can determine that a female is at risk for preterm labor and preterm delivery, and that the infant&#39;s chances for survival would be small, then the practitioner can advise the female of the risk. Accordingly, the female can make the decision to avoid pregnancy or can, with the assistance of her physician; take steps through diet, rest, and medications to lessen the risk of preterm labor.  
      As used herein the term “female” refers to a mammalian female, such as a human, horse, dog, cow, pig or monkey. Although the devices and methods are particularly adapted for use in a human female, one skilled in the art understands that they may be used in any female mammal. Accordingly, the devices and methods of the present invention could be used in veterinary medicine, if desired. When used in veterinary medicine, the devices and methods are specifically adapted for the type of animal on which the devices and methods will be used. For example, a device of the present invention adapted for equine use will include a hollow member and a measurement member that is greater in length relative to a device adapted for human use. The hollow member and the measurement member must both be of a sufficient length to enable a veterinarian to measure the length of the cervix, the dilation of the cervix, and the depth of the uterus of a female horse. Since the equine vaginal canal is longer than a human vaginal canal, both the hollow member and the measurement member of the devices of the present invention must accordingly be longer when adapted for equine use.  
     EXAMPLE I  
     Cervix Length Measurement  
      This example provides measurement of the length of the cervix in the vagina in a subject and correlation with reported criteria for determining the risk of preterm delivery.  
      The subject preferably lies in a prone position on her back. In one procedure, the practitioner uses a speculum to first examine the vaginal cavity and to observe the optimum position for placing the device. The practitioner then inserts into the vagina a device that includes a measurement member having a distal region and a proximal region, a hollow member through which the measurement member is inserted and advanced, and a flange engaged to the distal end of the hollow member. Alternatively, the practitioner may insert the device into the vagina without first using the speculum. The flange of the device has a surface adapted to contact the cervix at the external uterine opening after the distal end of the hollow member is inserted into the vagina. The practitioner next advances the hollow member within the vagina until the flange contacts the cervix at the external uterine opening. At this point, forward progress of the hollow member is prevented. The practitioner then progresses the measurement member through the hollow member until the distal region of the measurement member contacts the cervical-uterine junction at the fornix vaginae. Subsequently, the practitioner determines the length of the cervix in the fornix vaginae by observing the position of the proximal end of the hollow member along a measurement scale located on the proximal portion of the measurement member. Since the length of the cervix in the fornix vaginae is inversely related to the risk of preterm delivery, the practitioner is then able to determine that risk in the patient. The practitioner uses the data provided herein in Table  1 , discussed in Iams et al.,  N. Eng. J. Med.  334:567 (1996); which is incorporated by reference herein, in order to determine the relative risk of preterm delivery.  
               TABLE I                          Relative Risk of Preterm Delivery                                     Length of cervix                       (mm)   Percentile   at 24 weeks   at 28 weeks                                                 40   ≦75   2   2.8           35   ≦50   2.4   3.5           30   ≦25   3.8   5.4           26   ≦10   6.2   9.6           22   ≦5   9.5   13.9           13   ≦1   14   24.9                      
 
      As used herein, the term “relative risk” refers to the likelihood that there will be a preterm delivery when compared to the population that does not have that finding. In this subject, the length of the cervix is determined to be 22 mm. Since the subject is at 24 weeks of gestation, the relative risk for preterm delivery for this subject is 9.5. In other words, this subject has a 9.5 higher risk for preterm delivery than an individual whose cervix is greater than 22 mm in length.  
     EXAMPLE II  
     Cervix Dilation Measurement  
      This example demonstrates the use of the invention disclosed herein to measure the dilation of the cervix uteri in the same subject as in Example 1, to predict the risk for preterm delivery or the particular stage of delivery in a normal pregnancy.  
      One of the devices of the present invention is used to measure the dilation of the cervix uteri. A physician inserts into the vagina a device that includes a measurement member having a distal region and a proximal region, a hollow member through which the measurement member is inserted and advanced, and a flange engaged to the distal end of the hollow member. The flange of the device has a surface adapted to contact the cervix after the distal end of the hollow member is inserted into the vagina, includes a measurement scale, and is substantially translucent. Also, the flange is preferably off-set to the side of the hollow member to allow the flange to cover the external uterine opening while also allowing for the further advancement of the measurement member toward the fornix. The device is advanced within the vagina until the flange contacts the cervix at the external uterine opening. The physician then measures the dilation of the cervix by comparing the dilation of the cervix with the measurement scale on the flange. Using this procedure, the dilation of the cervix uteri is this subject is found to be 5 cm. Accordingly, the physician advises the subject that delivery is imminent. Since this subject is in her 24 th  week of pregnancy, this delivery is premature or preterm.  
      Although the invention has been described with reference to the examples provided above, it should be understood that various modifications can be made without departing from the spirit of the invention. Accordingly, the invention is limited only by the claims.