Abstract:
A device for measuring a length of a cervix includes an elongate measurement member, a hollow member, a flange, a handle, and a locking mechanism. The elongate measurement member extends along a longitudinal axis and includes a measurement scale thereon. The hollow member is coaxial with and disposed over the elongate measurement member. The flange is offset from the longitudinal axis and attached to a distal end of the hollow member. The handle is attached to a proximal end of the measurement member. The locking mechanism is configured, when locked, to fix the hollow member relative to the measurement member and, when unlocked to allow the hollow member to slide along the measurement member and rotate about the longitudinal axis so as to place the flange in a desired position without moving the measurement scale.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/260,520, filed Nov. 12, 2009, entitled “Devices and Methods for Cervix Measurement.” This application also claims priority to U.S. Provisional Patent Application No. 61/369,523, filed Jul. 30, 2010, entitled “Devices and Methods for Cervix Measurement.” These applications are herein incorporated by reference in their entirety. 
     
    
     INCORPORATION BY REFERENCE 
       [0002]    All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. 
       FIELD OF THE INVENTION 
       [0003]    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 formix vaginae and the dilation of the cervix uteri. 
       BACKGROUND OF THE INVENTION 
       [0004]    Preterm labor, or labor before 37 weeks gestation, has been reported in approximately 12.8 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 formix vaginae and the risk of preterm labor has also been observed. Andersen et al., Am. J. Obstet. Gynecol. 163:859 (1990); tarns et al., N. Eng. J. M. 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 formix vaginae as part of normal prenatal care in order to assess risk of preterm labor. 
         [0005]    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 diameter 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. 
         [0006]    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 if 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. 
         [0007]    Cervical incompetence is a well recognized clinical problem. Several investigators have reported evidence of increased internal 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. 
         [0008]    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 a 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 which 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. 
         [0009]    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 a measuring the length of the cervix would be predictive for preterm labor. 
         [0010]    Currently, a physician has at least two options to measure the length of the cervix in the formix 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 formix. 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, digital 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 to the fetus itself. 
         [0011]    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. Additionally, there is a risk that the probe that must be inserted into the vagina as part of the procedure may cause injury if not inserted with care. Also, due to the expense of the procedure many women, especially those without proper health insurance, cannot afford to have a sonographic test performed. 
         [0012]    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 formix 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 formix 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; 4,685,474; and 5,658,295 suffer from similar problems due to their use of expandable wings or divergeable 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 formix vaginae because of the lack of an appropriate measuring scale and a stop for automatically recording the measurement. 
         [0013]    There exists a need for a simple and inexpensive device that can be used to determine the length of the cervix in the formix 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 sterile and disposable. In addition, it is desirable that device be able to lock after a measurement is taken to ensure that the measurement does not change between the time a user takes the measurement and removes the device from the patient to read the measurement. The present invention satisfies these needs and provides related advantages as well. 
       SUMMARY OF THE INVENTION 
       [0014]    In general, in one aspect, a device for measuring a length of a cervix includes an elongate measurement member, a hollow member, a flange, a handle, and a locking mechanism. The elongate measurement member extends along a longitudinal axis and includes a measurement scale thereon. The hollow member is coaxial with and disposed over the elongate measurement member. The flange is offset from the longitudinal axis and attached to a distal end of the hollow member. The handle is attached to a proximal end of the measurement member. The locking mechanism is configured, when locked, to fix the hollow member relative to the measurement member and, when unlocked to allow the hollow member to slide along the measurement member and rotate about the longitudinal axis so as to place the flange in a desired position without moving the measurement scale. 
         [0015]    This and other embodiments can include one or more of the following features. The proximal end of the hollow member can be slideable into the handle. The flange can have an opening through which the measurement member can advance distally. The flange can have a flat surface perpendicular to the longitudinal axis. The locking mechanism can include a button, the button including a through-hole configured such that the hollow member can slide therethrough and a lock channel configured such that the hollow member cannot slide therethrough. The button can further include at least one lock ramp between the through-hole and the lock channel. The measurement scale can be a millimeter scale. The measurement scale can extend from 0 mm to 50 mm. The hollow member can be transparent. The measurement scale can include an opaque background. The device can further include an indicator line on the hollow member. The indicator line can be a color other than black. 
         [0016]    In general, in one aspect, a method for measuring a length of a cervix includes: holding a handle of a device, the device further including an elongate measurement member having a measurement scale thereon, a hollow member coaxial with and disposed over the elongate measurement member, and a flange attached to a distal end of the hollow member; rotating the hollow member about the elongate measurement member so as to place the flange at a desired orientation without rotating the measurement scale; advancing the device distally within a vagina until the flange contacts a cervix at an external uterine opening; advancing the measurement member distally within the vagina until a distal end of the measurement member contacts a cervical uterine junction at a formix vaginae; locking the measurement member relative to the hollow member by locking a locking mechanism on the handle; and observing a position of the hollow member with respect to the measurement member to determine a length of the cervix in the formix vaginae. 
         [0017]    This and other embodiments can include one or more of the following features. Advancing the measurement member distally can include sliding the hollow member into the handle. The flange can be offset from a longitudinal axis of the measurement member. The locking mechanism can include a button having a through-hole and a lock channel, and wherein locking the locking mechanism comprises pushing the button such that the hollow member moves into the lock channel and cannot slide through the through-hole. Observing the position can include observing an indicator line on the hollow member with respect to a measurement scale on the measurement member. The method can further include determining the risk of miscarriage based upon the length of the cervix in the formix vaginae, wherein the length of the cervix in the formix vaginae is inversely related to the risk of miscarriage. The method can further include predicting the ease of inducing labor, wherein the length of the cervix in the formix vaginae is inversely related to the ease of inducing labor. The method can further include determining the risk of preterm labor based upon the length of the cervix in the formix vaginae, wherein the length of the cervix in the formix vaginae is inversely related to the risk of preterm labor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The novel features of the invention are set forth with particularity in the claims that follow. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which: 
           [0019]      FIG. 1   a  is an illustration of a measuring device, according to one embodiment. 
           [0020]      FIGS. 1   b - 1   e  are additional views of the measuring device of  FIG. 1   a.    
           [0021]      FIG. 2   a  is an illustration of a measuring device, according to one embodiment. 
           [0022]      FIGS. 2   b - 2   e  are additional views of the measuring device of  FIG. 2   a.    
           [0023]      FIG. 3   a  is an illustration of a measuring device, according to one embodiment. 
           [0024]      FIGS. 3   b - 3   d  are additional views of the measuring device of  FIG. 3   a.    
           [0025]      FIG. 4   a  is an illustration of a measuring device, according to one embodiment. 
           [0026]      FIGS. 4   b - 4   g  are additional views of the measuring device of  FIG. 4   a.    
           [0027]      FIG. 5   a  is an illustration of a measuring device, according to one embodiment. 
           [0028]      FIGS. 5   b - 5   d  are additional views of the measuring device of  FIG. 5   a.    
           [0029]      FIG. 6   a  is an illustration of a measuring device, according to one embodiment. 
           [0030]      FIGS. 6   b - 6   f  are additional views of the measuring device of  FIG. 6   a.    
           [0031]      FIG. 7   a  is an illustration of a measuring device, according to one embodiment. 
           [0032]      FIGS. 7   b - 7   h  are additional views of the measuring device of  FIG. 7   a.    
           [0033]      FIG. 8  is an illustration of a measuring device in use for measuring the vaginal cervix. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]    The present invention provides various devices and methods for determining dimensions of female reproductive organs. For example, the devices described herein are particularly adapted for determining the length of the cervix in the formix vaginae, which, as described above, is related to the risk of preterm labor in an individual. The devices can also be suited for determining the dilation of the cervix uteri, for predicting the risk of preterm labor or the particular stage of delivery. 
         [0035]    It is, however, contemplated herein, that the invention is not limited to determining various dimensions of female reproductive organs. For example, the invention can be 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. 
         [0036]    The devices described herein are also preferably fabricated from relatively inexpensive materials and the measurement is quick to perform. This 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 can record 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 can be accomplished by the use of a flange to stop progression of the hollow member of the device while still allowing the measurement member to be advanced within the body. 
         [0037]      FIG. 1   a  illustrates a measuring device  100  that includes an elongated measurement member  102  and an elongated hollow member  104 . The elongated measurement member  102  is adapted to be inserted into the hollow member  104 , and specifically into a lumen of the hollow member. Handle  106  can be positioned on a proximal portion of the measuring device, as shown in  FIG. 1   a . In one embodiment, the handle is molded from the same material as the measurement member  102 . In other embodiments, the handle can be a rubber or foam component that is fitted on to and over the proximal end of the measuring device. 
         [0038]    A measurement scale  108  can be disposed along a portion of the measurement member  102 . The measurement scale  108  can include any number of a series of visual markings on the measurement member  102  which relate a measurement or distance. In a particularly preferred embodiment, the measurement scale  108  includes a plurality of millimeter (mm) incremental markings and a plurality of centimeter (cm) incremental markings. 
         [0039]    As shown in  FIG. 1   a , the measurement scale  108  can be color-coded to indicate the relative risks of preterm delivery for a cervix length falling within each respective colored region. For example, in one embodiment, a first zone  132  can include the incremental markings less than 2 cm and can be coded in a first color, such as red, a second zone  134  can include the incremental markings from 2 to 3 cm and can be coded in a second color, such as yellow, and the third zone  134  can include the incremental markings from 3 to 5 cm and can be coded in a third color, such as green. In  FIG. 1   a , the measurement scale 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. For instance, the first zone  132  indicates a shorter cervix, and therefore a higher risk of preterm delivery, than the second zone  134 , which indicates a cervix length that reflects a higher risk of preterm delivery than the green zone  136 . 
         [0040]    A flange  110  that is shaped for non-abrasive contact with tissue can be disposed on a distal portion of measuring device  100 . The flange can be preferably flat and spherically or conically shaped. Alternatively, however, the flange 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 the flange is also preferably offset from the longitudinal axis of the measuring device  100 . Additionally, the flange can include an opening  112  through which measurement member  102  may be advanced distally after the flange contacts a bodily surface. Preferably, the flange 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 may be formed as an integral component of the hollow member  104 . 
         [0041]      FIGS. 1   b - 1   d  illustrate the operation of the measuring device  100  as it is used to measure the length of a cervix. When the distal end of the measurement member  102  is flush with the flange, as shown in  FIG. 1   b , the device is in a starting configuration. The device  100  can be advanced into the vagina until the flange  110  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  110  and the end of the cervix at the external uterine opening. Since flange  110  is preferably offset from the longitudinal axis of measuring device  100 , in one embodiment the flange is placed both in contact with the end of the cervix and also covering the external uterine opening. As a result, the device can oriented so that measurement member  102  is still able to be progressed within the formix, rather than being advanced through the uterus, since the body of flange  106  is, with this method, covering the external uterine opening. 
         [0042]    Subsequently, as shown in  FIGS. 1   c - 1   d , a distal portion of measurement member  102  can continue to be advanced through opening  112  of flange  110  until the distal end contacts a wall of the body, such as, e.g., the anterior formix. When the distal end of the measurement member is advanced beyond the flange the device is in a measuring configuration.  FIG. 1   c  shows a side view of the measurement member in the measuring configuration, and  FIG. 1   d  shows a top down view of the device in the measuring configuration. It can be seen in  FIG. 1   d , for example, that the measurement member has been advanced 4 cm beyond the flange. The length of the cervix can then be measured by observing the position of the proximal end of the hollow member  104  along the measurement scale  108  of the measurement member  102 . In another embodiment, a method of measurement comprises advancing the distal end of the measurement member  102  to the wall of the body, such as the anterior formix, and then advancing the hollow member  104  so that the flange  110  is placed into contact with the end of the cervix at the external uterine opening. 
         [0043]    Referring now to  FIG. 1   e , a locking mechanism  114  can be located on the measuring device  100  that allows a user to secure the measurement member  102  within the hollow member  104  after the measurement of a body part, such as, e.g., the length of the cervix. In  FIG. 1   e , the locking mechanism  114  includes button  116 , cantilever arm  118 , detents  120 , and opening  122 . When the locking mechanism is in the locked configuration, as shown in  FIG. 1   e , the cantilever arm  118  engages detents  120  on the inside of hollow member  104 . The cantilever arm can be integral to the measurement member  102 , for example. To allow sliding of the measurement member within the hollow member, button  116  can be pressed inwards towards opening  122 , causing cantilever arm  118  to disengage detents  120  and allow sliding. 
         [0044]    For example, to take a measurement of a body part, a user can insert the measuring device  100  into the patient. The user can then press the button  116  inwards to disengage the cantilever arm and allow the measurement member to slide within the hollow member. After the measurement of a body part is taken with the device, the user can release the button, causing the cantilever arm to engage the detents and lock the position of the measurement member  102  within the hollow member  104 . This allows the user to remove the device from the patient to read the measurement scale while ensuring that movement of the measurement member  102  proximally or distally within the hollow member  104  is prevented. 
         [0045]    During a measurement procedure, a user can hold handle  106  with the dominant hand like a dart, and can hold the barrel of the hollow member  104  with the non-dominant hand. The user can activate button  116  with the dominant hand to temporarily unlock the measuring device, allowing the hollow member to slide with respect to the measurement member. 
         [0046]    Referring now to  FIG. 2   a , another embodiment of a measuring device  200  is shown. Measuring device  200  includes many of the features of measuring device  100 , described above and illustrated in  FIGS. 1   a - 1   e . For example, measuring device  200  includes an elongated measurement member  202  slidably disposed within an elongated hollow member  204 . Handle  206  can be positioned on a proximal portion of the measuring device, and measurement scale  208 , such as a color-coded measurement scale, can be disposed on the measurement member  202 . The measuring device can further include a flange  210  on a distal portion of the device, and an opening  212  that allows the measurement member  202  to extend distally beyond the hollow member  204 . 
         [0047]    As described above, the device  200  can have a starting configuration, as shown in  FIG. 2   b , and a measuring configuration, as shown in  FIG. 2   c . The measuring device  200  can further include a locking mechanism  214 . The locking mechanism allows a user to lock the measurement member  202  within the hollow member  204 , to prevent movement of the measurement member with respect to the hollow member after a measurement is taken. In the embodiment shown in  FIGS. 2   a - 2   e , the locking mechanism  214  is disposed on the hollow member  204 . 
         [0048]    Referring now to  FIG. 2   d , which is a side view of the locking mechanism  214 , and  FIG. 2   e , which is a cross sectional view of the locking mechanism  214 , the locking mechanism can further include pads or buttons  216 , tabs  218 , and detents  220 . The buttons  216  and tabs  218  can be integral to the hollow member  204 , and the detents  220  can be integral to the measurement member  202 , for example. In the embodiment shown in  FIGS. 2   d - 2   e , the locking mechanism includes two buttons  216 . However, in other embodiments, the locking mechanism can include only a single button, or alternatively, can include more than two buttons. 
         [0049]    When the locking mechanism  214  is in a locked configuration, as shown in  FIG. 2   d , the tabs engage detents  220 , preventing any movement of the measurement member with respect to the hollow member  204 . However, when the buttons  216  are depressed inwards by a user, as shown in  FIG. 2   e , the tabs  218  can be squeezed outwards, as indicated by arrows  224 , causing them to disengage from detents  220 . This allows a measurement to be taken by sliding the measurement member  202  within the hollow member  204 . 
         [0050]    To take a measurement of a body part, a user can insert the measuring device  200  into the patient. The user can then press the button or buttons  216  inwards to cause the tabs  218  to squeeze outwards disengaging detents  220 , thereby allowing the measurement member to slide within the hollow member. After the measurement of a body part is taken with the device, the user can release the buttons, causing the tabs to engage the detents and lock the position of the measurement member  202  within the hollow member  204 . This allows the user to remove the device from the patient to read the measurement scale while ensuring that movement of the measurement member  202  proximally or distally within the hollow member  204  is prevented. 
         [0051]    During a measurement procedure, a user can hold handle  206  with the dominant hand like a dart, and can hold the barrel of the hollow member  204  with the non-dominant hand. The user can activate button  216  with the non-dominant hand to temporarily unlock the measuring device, allowing the hollow member to slide with respect to the measurement member. 
         [0052]    Referring now to  FIG. 3   a , yet another embodiment of a measuring device  300  is shown. Measuring device  300  includes many of the features of measuring device  100 , described above and illustrated in  FIGS. 1   a - 1   e . For example, measuring device  300  includes an elongated measurement member  302  slidably disposed within an elongated hollow member  304 . Handle  306  can be positioned on a proximal portion of the measuring device, and measurement scale  308 , such as a color-coded measurement scale, can be disposed on the measurement member  302 . The measuring device can further include a flange  310  on a distal portion of the device, and an opening  312  that allows the measurement member  302  to extend distally beyond the hollow member  304 . 
         [0053]    As described above, the device  300  can have a starting configuration, as shown in  FIG. 3   b , and a measuring configuration, as shown in  FIG. 3   c . In addition, a locking mechanism  314  can be located on the measuring device  300  that allows a user to secure the measurement member  302  within the hollow member  304  after the measurement of a body part, such as, e.g., the length of the cervix. 
         [0054]    In  FIG. 3   d , the locking mechanism  314  includes button  316 , cantilever arm  318 , and detents  320 . When the locking mechanism is in the locked configuration, as shown in  FIG. 3   d , the cantilever arm  318  engages detents  320  on the outside of measurement member  302 . The cantilever arm can be integral to the hollow member  304 , for example. To allow sliding of the measurement member within the hollow member, button  316  can be pressed inwards, causing cantilever arm  318  to disengage detents  320  and allow sliding. 
         [0055]    For example, to take a measurement of a body part, a user can insert the measuring device  300  into the patient. The user can then press the button  316  inwards to disengage the cantilever arm and allow the measurement member to slide within the hollow member. After the measurement of a body part is taken with the device, the user can release the button, causing the cantilever arm to engage the detents and lock the position of the measurement member  302  within the hollow member  304 . This allows the user to remove the device from the patient to read the measurement scale while ensuring that movement of the measurement member  302  proximally or distally within the hollow member  304  is prevented. 
         [0056]    During a measurement procedure, a user can hold handle  306  with the dominant hand like a dart, and can hold the barrel of the hollow member  304  with the non-dominant hand. The user can activate button  316  with the non-dominant hand to temporarily unlock the measuring device, allowing the hollow member to slide with respect to the measurement member. 
         [0057]    Referring now to  FIG. 4   a , another embodiment of a measuring device  400  is shown. Measuring device  400  includes many of the features of measuring device  100 , described above and illustrated in  FIGS. 1   a - 1   e . For example, measuring device  400  includes an elongated measurement member  402  slidably disposed within an elongated hollow member  404 . Handle  406  can be positioned on a proximal portion of the measuring device, and measurement scale  408 , such as a color-coded measurement scale, can be disposed on the measurement member  402 . The measuring device can further include a flange  410  on a distal portion of the device, and an opening  412  that allows the measurement member  402  to extend distally beyond the hollow member  404 . 
         [0058]    As described above, the device  400  can have a starting configuration, as shown in  FIG. 4   b , and a measuring configuration, as shown in  FIG. 4   c . In contrast to the embodiments described above, the hollow member  404  of the measuring device  400  in  FIGS. 4   a - 4   e  slides into the handle  406  when a measurement is taken. The measurement member  402  remains fixed in position with respect to the handle, which allows the measurement member to extend distally beyond the flange  410  during measurements. 
         [0059]    The measuring device  400  can further include a locking mechanism  414 . The locking mechanism allows a user to lock the hollow member  404  within the handle  406 , to prevent movement of the hollow member with respect to the measurement member after a measurement is taken. In the embodiment shown in  FIGS. 4   a - 4   e , the locking mechanism  414  can comprise a button  416  with a through-hole (not shown). In  FIG. 4   d , the device is shown in an unlocked configuration, in which the through-hole is aligned with the hollow member  404  to allow the hollow member to travel therethrough. When the device is in a locked configuration, as shown in  FIG. 4   e , the through-hole pushes against the hollow member, preventing movement of the hollow member with respect to the measurement member. 
         [0060]      FIG. 4   f  shows a cross-sectional view of locking mechanism  414 , button  416 , and hollow member  404 . The button geometry is designed to operate smoothly with a low actuation force to engage the locking mechanism. The open channel  418  of the button allows the hollow member  404  to slide freely into the handle when a measurement is being taken. When the button is depressed, the lock ramps  420  are forced to slide over the hollow member  404 , which provides tactile and audible feedback that the device is in the locked position. The design of the lock ramps, including height and ramp angle affects the effort levels required to activate the button. The width of the lock channel  422  is designed to be narrower than the overall outside diameter of the hollow member  404 , so that the interference between the two surfaces provides a retention force to maintain the measurement while the device is removed from the patient. In some embodiments, the locking mechanism does not include the lock ramps  420 . In other embodiments, the lock channel  422  can be tapered to provide a frictional, locking fit for hollow member  404  when button  416  is depressed, as shown in  FIG. 4   g.    
         [0061]    For example, to take a measurement of a body part, a user can insert the measuring device  400  in an unlocked configuration (e.g., where the through-hole is aligned to allowed movement of the hollow member) into the patient. After the measurement of a body part is taken with the device, the user can press the button  416 , causing the through-hole to press against the hollow member to prevent movement of the hollow member. This allows the user to remove the device from the patient to read the measurement scale while ensuring that movement of the measurement member  402  proximally or distally within the hollow member  404  is prevented. 
         [0062]    During a measurement procedure, a user can hold handle  406  with the dominant hand like a dart, and can hold the barrel of the hollow member  104  with the non-dominant hand. After taking a measurement, the user can activate button  416  with the dominant hand to lock the measuring device, preventing the hollow member from sliding with respect to the measurement member. 
         [0063]    Referring now to  FIG. 5   a , another embodiment of a measuring device  500  is shown. Measuring device  500  includes many of the features of measuring device  100 , described above and illustrated in  FIGS. 1   a - 1   e . For example, measuring device  500  includes an elongated measurement member  502  slidably disposed within an elongated hollow member  504 . Syringe-style handle  506  can be positioned on a proximal portion of the measuring device, and measurement scale  508 , such as a color-coded measurement scale, can be disposed on the measurement member  502 . The measuring device can further include a flange  510  on a distal portion of the device, and an opening  512  that allows the measurement member  502  to extend distally beyond the hollow member  504 . 
         [0064]    As described above, the device  500  can have a starting configuration, as shown in  FIG. 5   b , and a measuring configuration, as shown in  FIG. 5   c . Similar to the embodiment of measuring device  400  described above and illustrated in  FIGS. 4   a - 4   e , the hollow member  504  of the measuring device  500  in  FIGS. 5   a - 5   d  slides into the handle  506  when a measurement is taken. The measurement member  502  remains fixed in position with respect to the handle, which allows the measurement member to extend distally beyond the flange  510  during measurements. 
         [0065]    The measuring device  500  can further include a locking mechanism  514 . The locking mechanism allows a user to lock the hollow member  504  within the handle  506 , to prevent movement of the hollow member with respect to the measurement member after a measurement is taken. In the embodiment shown in  FIG. 5   d , the locking mechanism  514  can comprise a button  516  with a through-hole (not shown). Similar to the embodiments described above in  FIGS. 4   a - 4   e , the device can have an unlocked configuration, in which the through-hole is aligned with the hollow member  504  to allow the hollow member to travel therethrough. The device can also have a locked configuration, in which the through-hole pushes against the hollow member thereby preventing movement of the hollow member with respect to the measurement member. 
         [0066]    To take a measurement of a body part, a user can insert the measuring device  500  in an unlocked configuration (e.g., where the through-hole is aligned to allowed movement of the hollow member) into the patient. After the measurement of a body part is taken with the device, the user can press the button  516 , causing the through-hole to press against the hollow member to prevent movement of the hollow member. This allows the user to remove the device from the patient to read the measurement scale while ensuring that movement of the measurement member  502  proximally or distally within the hollow member  504  is prevented. In  FIG. 5   d , the measurement scale is read at point  526  on the handle when taking the measurement, for example. 
         [0067]    During a measurement procedure, a user can hold syringe-style handle  506  with the dominant hand like a syringe, and can hold the barrel of the hollow member  504  with the non-dominant hand. After taking a measurement, the user can activate button  516  with the dominant or non-dominant hand to lock the measuring device, preventing the hollow member from sliding with respect to the measurement member. 
         [0068]    Referring now to  FIG. 6   a , another embodiment of a measuring device  600  is shown. Measuring device  600  includes many of the features of measuring device  100 , described above and illustrated in  FIGS. 1   a - 1   e . For example, measuring device  600  includes an elongated measurement member  602  slidably disposed within an elongated hollow member  604 . Handle  606  can be positioned on a proximal portion of the measuring device, and measurement scale  608 , such as a color-coded measurement scale, can be disposed on the measurement member  602 . The measuring device can further include a flange  610  on a distal portion of the device, and an opening  612  that allows the measurement member  602  to extend distally beyond the hollow member  604 . 
         [0069]    As described above, the device  600  can have a starting configuration, as shown in  FIG. 6   b , and a measuring configuration, as shown in  FIG. 6   c . The measuring device  600  can further include a locking mechanism  614 . The locking mechanism allows a user to lock the measurement member  602  within the hollow member  604 , to prevent movement of the measurement member with respect to the hollow member after a measurement is taken. In the embodiment shown in  FIGS. 6   a - 6   f , the locking mechanism  614  is disposed on the hollow member  204 . 
         [0070]    Referring now to  FIG. 6   d , which is a cross sectional view of the locking mechanism  614 , the locking mechanism can further an annular snap  628 . The measurement member  602  also has an annular snap  630  that corresponds to the annular snap  628  on the locking mechanism. When the locking mechanism is in an unlocked configuration, as shown in  FIG. 6   d , the annular snaps  628  and  630  are not in contact, so there is some play between the locking mechanism  614  and the measurement member  602 , which allows the measurement member to slide freely within the hollow member  604 . As a user rotates the locking mechanism, as shown in  FIG. 6   e , the annular snaps contact each other, providing the user with tactile feedback of locking. In  FIG. 6   f , the locking mechanism is shown in a locked configuration, with the annular snaps contacting each other on both sides. When the annular snaps are in contact as shown in  FIG. 6   f , there is no play between the hollow member and the measurement member, which prevents movement of the hollow member with respect to the measurement member. 
         [0071]    To take a measurement of a body part, a user can insert the measuring device  600  into the patient in the unlocked configuration. After the measurement of a body part is taken with the device, the user can rotate the locking mechanism  614 , causing the annular snaps to engage each other on both sides to lock the position of the measurement member  602  within the hollow member  604 . This allows the user to remove the device from the patient to read the measurement scale while ensuring that movement of the measurement member  602  proximally or distally within the hollow member  604  is prevented. 
         [0072]    During a measurement procedure, a user can hold handle  606  with the dominant hand like a dart, and can hold the locking mechanism  614  with the non-dominant hand. After taking a measurement, the user can rotate the locking mechanism with the non-dominant hand until the annular snaps engage each other to lock the measuring device, preventing the hollow member from sliding with respect to the measurement member. The user can also hold steady the locking mechanism  614  with the non-dominant hand and rotate the handle  606  with the dominant hand until the annular snaps engage each other to lock the measuring device. The relative motion of the locking mechanism  614  and the handle  606  is what engages the locking mechanism, regardless of which is held in place and which is rotated. 
         [0073]    Referring now to  FIG. 7   a , another embodiment of a measuring device  700  is shown. Measuring device  700  includes many of the features of measuring device  100 , described above and illustrated in  FIGS. 1   a - 1   e . For example, measuring device  700  includes an elongated measurement member  702  slidably disposed within an elongated hollow member  704 . The measuring device can further include a flange  710  on a distal portion of the elongated hollow member  704 , and an opening  712  that allows the measurement member  702  to extend distally beyond the hollow member  704 . Handle  706  can be positioned on a proximal portion of the measuring device and can be attached to the measurement member and measurement scale  708  can be disposed on the measurement member  702 . As shown in  FIG. 7   f , the measurement scale can be a millimeter sale, with markings from 0-50 mm, marked in 5 mm increments. Moreover, the background  732  for the measurement scale  708  can be opaque. For example, the measurement member  702  can be composed of an opaque material or an opaque coating can cover the portion of the measurement member  702  on which the measurement scale  708  is printed. An opaque background for the measurement scale can allow for easier readability of the numbers on the scale. Further, the hollow member  704  can be transparent and include an indicator line  734  that is colored, e.g., blue, to help contrast it from the measurement scale. Contrasting the indicator line  734  with the measurement scale allows for easier readability of the final measurement. 
         [0074]    As described above, the device  700  can have a starting configuration, as shown in  FIG. 7   b , and a measuring configuration, as shown in  FIG. 7   c . Similar to the embodiment of measuring device  400  described above and illustrated in  FIGS. 4   a - 4   e , the hollow member  704  of the measuring device  700  in  FIGS. 7   a - 7   d  slides into the handle  706  (or, alternatively, the handle  706  slides over the hollow member  704 ) when a measurement is taken. The measurement member  702  remains fixed in position with respect to the handle, which allows the measurement member to extend distally beyond the flange  710  during measurements. As shown in  FIGS. 7   g  and  7   h , the elongated hollow member  704  can be free to rotate with respect to the handle  706  and the measurement member  702  ( FIG. 7   g  shows the flange  710  extending parallel to the page, while  FIG. 7   h  shows the flange  710  extending out of the page). Such free rotation allows for the accommodation of any measurement technique, e.g. right or left-handed measurements, while still allowing for proper placement of the flange  710 . That is, rotation of the hollow member  702  to place the flange  710  in a desired position allows the measurement scale to remain in place, i.e., facing the user. Maintaining the measurement scale directed towards the users ensures that the user is more easily able to read and determine the measured length. 
         [0075]    The measuring device  700  can further include a locking mechanism  714 . The locking mechanism allows a user to lock the hollow member  704  within the handle  706 , to prevent rotational or longitudinal movement of the hollow member with respect to the measurement member after a measurement is taken. In the embodiment shown in  FIG. 7   d , the locking mechanism  714  can comprise a button  716  with a through-hole (not shown). Similar to the embodiments described above in  FIGS. 4   a - 4   e , the device can have an unlocked configuration, in which the through-hole is aligned with the hollow member  704  to allow the hollow member to travel therethrough. The device can also have a locked configuration, in which the through-hole pushes against the hollow member thereby preventing movement of the hollow member with respect to the measurement member. 
         [0076]    To take a measurement of a body part, a user can hold the handle  706  with the dominant hand and can hold the hollow member  704  with the non-dominant hand. The user can orient the measuring scale  708  such that it faces the user and can then rotate the hollow member  704  such that the flange  710  is properly oriented with respect to the patient. Because the hollow member  704  is transparent, the measuring scale  708  can be viewed through the hollow member  704 . 
         [0077]    The measuring device  700  can be inserted in an unlocked configuration (e.g., where the through-hole is aligned to allowed movement of the hollow member) into the patient. After the measurement of a body part is taken with the device, as described above, the user can press the button  716 , causing the through-hole to press against the hollow member to prevent movement of the hollow member. This allows the user to remove the device from the patient to better read the measurement scale while ensuring that movement of the measurement member  702  proximally or distally within the hollow member  704  is prevented. 
         [0078]    Referring to  FIG. 8 , the devices described herein can be used to measure the vaginal cervical length. The flange  810  (representing any of the flanges described herein) can be placed against the proximal wall of cervix  802 , while the measurement member  702  (representing any of the measurement members described herein) can be extended along the lateral wall of the cervix  802  until it is stopped by the vaginal formix  804 . The measurement member  702  and the flange  810  can then be locked with respect to one another such that the device&#39;s measurement scale can be used to determine the length as described above. 
         [0079]    As for additional details pertinent to the present invention, materials and manufacturing techniques may be employed as within the level of those with skill in the relevant art. The same may hold true with respect to method-based aspects of the invention in terms of additional acts commonly or logically employed. Also, it is contemplated that any optional feature of the inventive variations described may be set forth and claimed independently, or in combination with any one or more of the features described herein. Likewise, reference to a singular item, includes the possibility that there are plural of the same items present. More specifically, as used herein and in the appended claims, the singular forms “a,” “and,” “said,” and “the” include plural referents unless the context clearly dictates otherwise. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as “solely,” “only” and the like in connection with the recitation of claim elements, or use of a “negative” limitation. Unless defined otherwise herein, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The breadth of the present invention is not to be limited by the subject specification, but rather only by the plain meaning of the claim terms employed.