Abstract:
An instrument for measuring cervical dilation can have a pair of arms connected at their proximal ends to an arm pivot or articulating member, the arms being in movable communication with a gauge assembly for measuring the relative distance between the arms at a fixed location near the proximal ends of the arms. The arms can be disposed to apply an outward lateral pressure against the walls of the cervix, thereby engaging the cervix without the need for physical penetration, gripping, or other attachment of the device to the cervical tissue. Continuous outward lateral pressure of the arms against the cervical walls can allow the arms to expand in response to and in concert with expansion and dilation of the cervix. The relative distance between the arms correlates to the diameter of the cervix, such that the correlated measurement indicated on a scale of the gauge means is the measurement of cervical dilation.

Description:
CLAIM OF PRIORITY 
       [0001]    This patent application claims the benefit of priority of U.S. Provisional Patent Application Ser. No. 61/089,763, entitled CERVICAL DILATION METER, (Attorney Docket No. 2872.001PRV), filed on Aug. 18, 2008, which is hereby incorporated by reference herein in its entirety. 
     
    
     BACKGROUND 
       [0002]    The cervix is the portion of the uterus connecting the uterus to the vagina. The cervix is cylindrical or conical in shape, approximately one inch in length, and having a cervical canal passing through it with an external os opening to the vaginal cavity and internal os opening to the uterine cavity. During labor and delivery, the cervical canal is the channel through which the baby passes from the uterine cavity into the vaginal cavity. During labor, the position (station) of the cervix rotates from posterior to anterior 
         [0003]    During labor, in response to coordinated uterine contractions and pressure created by the descending fetal head, the length of the cervix shortens and the cervical walls thin in a process known as “effacement”, and the cervix opens further or dilates. Effacement can be quantified in percentage, from 0% (no change) to 100% (completely thinned). Cervical dilation can be quantified as the diameter of the cervical opening, e.g., in centimeters ranging from zero (0) to ten (10) centimeters. When the cervix dilates to ten (10) centimeters or greater, the cervical dilation can be deemed complete, and the patient can be encouraged to push the baby out. Before effacement and complete dilation, patients are encouraged not to push due to the risk of injury to both mother and baby. Effacement and dilation are critical indicators of the progress, or lack of progress, of labor. The degree and rate of effacement and dilation are monitored periodically during the first stage of labor. Slow or inadequate cervical dilation may indicate the need for administering a cervical ripening drug or applying a cervical dilating instruments or the need for surgical delivery. 
         [0004]    A digital palpation is currently the standard procedure clinicians (physician, nurse, mid-wife, etc.) use to measure the cervical diameter. In digital examination, the clinician inserts a gloved hand into the vagina and uses the middle and index fingers to palpate or probe the cervix and external cervical os. The fingertips palpate and locate the external cervical os and are then spread until the fingertips contact opposing walls of the cervix. The distance between the spread fingertips corresponds to the cervical diameter. Using the digital palpation approach, the degree of dilation of the cervical os is estimated without any means to confirm visually the spacing between the index and middle fingers while situated within the cervical os. 
         [0005]    During the course of labor in a patient, one or more clinicians perform, on average, ten digital examinations. However, digital examination provides only intermittent data for assessment of labor progression. Furthermore, the accuracy of digital examination is very subjective and may depend upon many factors, including the experience, judgment, and the size of the clinician&#39;s fingers, and error caused by the stretching of the cervix by the clinician&#39;s fingers. Although an individual clinician may achieve acceptable repeatability and accuracy using this method, it is normal to see a one (1) centimeter error or variation in measurement among serial measurements by the same clinician. If different clinicians examine the same patient during the course of labor, the inaccuracy of cervical dilation measurements increases due to inter-clinician variability. 
         [0006]    Inaccurate or inconsistent measurements of cervical dilation may hinder the early detection of dysfunctional labor or delivery complications. Furthermore, despite the use of gloves, digital examination increases the risk of infection of the fetal membranes (chorioamnionitis), the lining and/or muscle of the uterus (endomyometritis), or of the infant (neonatal sepsis). This risk increases significantly after the fetal membranes have ruptured, and the risk of infection correlates to the number of digital exams. For this reason, it is preferable to minimize the number of digital exams, particularly after the fetal membranes have ruptured. Other disadvantages of digital examination measurements to determine cervical dilation include the inability to monitor dilation continuously, the procedure may dislodge fetal or uterine monitors, and the procedure is embarrassing and causes even more discomfort to the mother who is already experiencing significant pain due to labor. 
         [0007]    Various mechanical and electrical systems have been devised to measure cervical dilation. See, e.g.,  Cervimetry: A Review of Methods for Measuring Cervical Dilation During Labor , Obstetrics &amp; Gynecology Survey, Vol. 55(5): 312-320 (2000); see also, e.g., Sharf Y, Farine D. et al.,  Continuous Monitoring of Cervical Dilation and Fetal Head Station During Labor , Medical Engineering &amp; Physics 29: 61-71 (2007). See also, e.g., the following U.S. patent Nos. and U.S. patent application Publication Nos.: U.S. Pat. Nos. 2,924,220; 3,768,459; 4,141,345; 4,207,902; 4,245,656; 4,476,871; 4,611,603; 4,682,609; 4,719,925; 5,222,485; 5,450,857; 5,658,295; 5,713,371; 5,935,061; 6,039,701; 6,066,104; 6,200,279; 6,270,458; 6,383,137; 6,419,646; 6,423,000; 6,423,016; 6,524,259; 6,540,977; 6,669,653; 6,802,917; 6,966,881; 6,994,678; 7,150,108; 7,207,941; US 2005/0049509; US 2006/0020230; US 2007/0156067; US 2007/0156068; US 2007/0179410; US 2007/0179410; US 2007/0213640; US 2008/0021350; and also PCT Patent Application Publications WO 1987/03189; WO 2000/051494; WO 2004/098375; WO 2004/00373. 
       SUMMARY/OVERVIEW 
       [0008]    The present inventors have recognized, among other things, that, unfortunately, none of the above-mentioned methods or devices have gained commercial acceptance for many reasons, including: patient discomfort and cervical tissue trauma due to attachment, penetration or active fixation engagement of the device to the cervical tissue (e.g., by needles, barbs, hooks, clamps, grips, or sutures); lack of accuracy due to cervical tissue distortion; inability to isolate measurement of cervical os dilation from measurement of changes in the station or movement of cervix during the progression of labor; blockage of the cervical canal (thus inhibiting descent of the fetal head and monitoring of fetal status and labor progression by known monitoring devices); complexity of the device or its installation; lack of disposability (thus high cost or a need to sterilize the device for later reuse in the patient); radiation, ultrasonic and electrical shock hazards; and unsuitability for patient ambulation or home use. Consequently, the present inventors have recognized and believe that there is currently no commercially available simple, objective mechanical monitoring device or system to measure cervical diameter, and digital examination continues to be the preferred method for measuring cervical diameter and dilation. 
         [0009]    Thus, the present inventors have recognized, among other things, the usefulness of an objective monitoring device that can accurately measure cervical dilation, that can differentiate cervical dilation from change in cervical station, that need not be invasive (need not penetrate tissue by barbs, needles, clips, sutures, or other invasive means) and need not grip, clamp or compress the cervix or otherwise distort the cervix. The present inventors have also recognized the usefulness of a device to monitor cervical dilation that can be placed and retained in the patient throughout the first stage of labor, thereby allowing continuous or ongoing monitoring of cervical dilation. The present inventors have also recognized the usefulness of a device for measuring cervical dilation that can remain in place in the patient without obstructing descent of the fetal head (which can inhibit delivery) and that can easily be displaced or expelled from the patient, such as by the natural progression of labor, without requiring manual removal by the clinician. The present inventors have also recognized the usefulness of a device that has a measurement scale that can be located outside the body and that can be simple enough to interpret that the patient or her family can directly monitor the patient&#39;s cervical dilation, without the need for clinician oversight. The present inventors have also recognized the usefulness of a cervical dilation monitoring device that can permit the patient to remain ambulatory while the device is in place. In certain examples, the present devices and methods can provide one or more of such useful characteristics in monitoring cervical dilation. To better illustrate the subject matter described herein, a non-limiting list of examples follows. 
         [0010]    Example 1 describes an apparatus comprising first and second arms, comprising respective proximal and distal portions, the proximal portions of the first and second arms coupled together, the distal portions of the first and second arms configured to be inserted between, and to exert enough of an outward force against, opposing lateral walls of a cervix or vagina to hold the apparatus in position, while measuring cervical dilation, without requiring active fixation to the cervix or vagina. In this example, a cervical dilation gauge assembly, communicatively coupled to the first and second arms to receive information about the cervical dilation, and comprising an external cervical dilation indicator to provide an indication of the cervical dilation to a user. 
         [0011]    In Example 2, the apparatus of Example 1 is optionally configured such that an intermediate region of the first arm comprises an outwardly bowed first cephalic curve, and wherein an intermediate region of the second arm comprises an outwardly bowed second cephalic curve, and wherein concave portions of the first and second cephalic curves are opposing each other. 
         [0012]    In Example 3, the apparatus of any one or any combination of Examples 1-2 is optionally configured such that the concave portions of the first and second cephalic curves are sized and shaped to receive and accommodate a fetal head therebetween. 
         [0013]    In Example 4, the apparatus of any one or any combination of Examples 1-3 is optionally configured such that the concave portions of the first and second cephalic curves are sized and shaped to receive a descending fetal head therebetween during birthing while the first and second arms continue to exert enough of an outward force against opposing lateral walls of a cervix or vagina to hold the apparatus in position while measuring cervical dilation without requiring active fixation to the cervix or vagina. 
         [0014]    In Example 5, the apparatus of any one or any combination of Examples 1-4 is optionally configured such that the first and second arms comprise respective first and second pelvic curves at or near a location between the intermediate and proximal portions of the respective first and second arms, such that the respective intermediate portions of the respective first and second arms angle or curve upward from the respective proximal portions of the respective first and second arms at an angle that is about 15 degrees to allow placement of the apparatus if the cervix is in a mid or anterior position. 
         [0015]    In Example 6, the apparatus of any one or any combination of Examples 1-5 optionally comprises a spring, providing a force that is coupled to the first and second arms to bias the first and second arms away from each other. 
         [0016]    In Example 7, the apparatus of any one or any combination of Examples 1-6 is optionally configured such that the spring is configured to exert enough of an outward force of the first and second arms against opposing lateral walls of the cervix or vagina to hold the apparatus in position while measuring cervical dilation without requiring active fixation to the cervix or vagina, and without exerting so much outward force so as to substantially affect the measuring of the cervical dilation. 
         [0017]    In Example 8, the apparatus of any one or any combination of Examples 1-7 is optionally configured such that distal portions of the respective first and second arms respectively comprise first and second feet that are respectively coupled to respective intermediate portions of the respective first and second arms by respective first and second flexible members that are respectively more flexible than the respective first and second feet and the respective intermediate portions of the respective first and second arms, and wherein the respective first and second feet flex at respective angles, with respect to the respective first and second arms, in a plane formed by intermediate portions of the first and second arms. 
         [0018]    In Example 9, the apparatus of any one or any combination of Examples 1-8 is optionally configured such that the first and second feet are respectively angled upward from a plane formed by the respective intermediate portions of the first and second arms by an angle that is about 30 degrees. 
         [0019]    In Example 10, the apparatus of any one or any combination of Examples 1-9 is optionally configured such that the first and second feet respectively provide a surface area of at least about 2.0 cm 2  for contacting the cervix. 
         [0020]    In Example 11, the apparatus of any one or any combination of Examples 1-10 optionally comprises a rotational pivot joint, coupling the proximal portions of the first and second arms together; and a spring, coupled to the first and second arms to exert an outward force to drive the first and second arms apart. 
         [0021]    In Example 12, the apparatus of any one or any combination of Examples 1-11 optionally is configured such that the spring is located at a proximal end of a member extending from a location near or distal to the rotational pivot joint to a more proximal external location. 
         [0022]    In Example 13, the apparatus of any one or any combination of Examples 1-12 is optionally configured such that the spring is located at the external location. 
         [0023]    In Example 14, the apparatus of any one or any combination of Examples 1-13 is optionally configured such that the member comprises a cable. 
         [0024]    In Example 15, the apparatus of any one or any combination of Examples 1-14 is optionally configured such that the member comprises a portion of a rack-and-pinion assembly. 
         [0025]    In Example 16, the apparatus of any one or any combination of Examples 1-15 is optionally configured such that the spring is located at the rotational pivot joint. 
         [0026]    In Example 17, the apparatus of any one or any combination of Examples 1-16 optionally comprises a stem including: a proximal portion coupled to the external indicator of cervical dilation; and a distal portion coupled to the proximal portion of at least one of the first and second arms. 
         [0027]    In Example 18, the apparatus of any one or any combination of Examples 1-17 optionally comprises an introducer sheath, sized and shaped to constrain the first and second arms toward each other during insertion of the apparatus, and to permit removal of the sheath over the stem. 
         [0028]    In Example 19, the apparatus of any one or any combination of Examples 1-18 optionally comprises a cable including a proximal portion coupled to the external indicator of cervical dilation, and a distal portion coupled to at least one of the first and second arms, and wherein the cable is constrained such that a position of a proximal end of the cable is correlative to the cervical dilation. 
         [0029]    In Example 20, the apparatus of any one or any combination of Examples 1-19 optionally comprises a spring, coupled to a proximal end of the cable, the spring configured to tend to move the proximal end of the cable in a proximal direction to exert, via the cable, a force on at least one of the first and second arms to tend to move respective portions of the first and second arms apart. 
         [0030]    Example 21 describes a method comprising: inserting first and second arms of a cervical dilation measuring apparatus into a vagina such that respective distal portions of the first and second arms exert enough of an outward force against, opposing lateral walls of a cervix or vagina to hold the apparatus in position, while measuring cervical dilation, without requiring active fixation to the cervix or vagina; communicating information about the cervical dilation to an external location; and providing an external indicator of the cervical dilation to a user, using the information. 
         [0031]    In Example 22, the method of Example 21 optionally comprises inserting first and second arms comprising respective outwardly bowed cephalic curves, wherein concave portions of the respective cephalic curves oppose each other. 
         [0032]    In Example 23, the method of any one or any combination of Examples 21-22 optionally comprises comprising receiving a fetal head between portions of the first and second arms. 
         [0033]    In Example 24, the method of any one or any combination of Examples 21-23 optionally comprises receiving a fetal head between portions of the first and second arms during birthing while the first and second arms continue to exert enough of an outward force against opposing lateral walls of a cervix or vagina to hold the apparatus in position while measuring cervical dilation without requiring active fixation to the cervix or vagina. 
         [0034]    In Example 25, the method of any one or any combination of Examples 21-24 optionally comprises placing the apparatus when the cervix is in a mid or anterior position such that respective intermediate portions of the respective first and second arms angle or curve upward from respective proximal portions of the respective first and second arms at an angle that is about 15 degrees. 
         [0035]    In Example 26, the method of any one or any combination of Examples 21-25 optionally comprises exerting enough of an outward force of the first and second arms against opposing lateral walls of the cervix or vagina to hold the apparatus in position while measuring cervical dilation without requiring active fixation to the cervix or vagina, and without exerting so much outward force so as to substantially affect the measuring of the cervical dilation. 
         [0036]    In Example 27, the method of any one or any combination of Examples 21-26 optionally comprises inserting into a cervical os first and second feet at respective distal portions of the first and second arms, such that the first and second feet flex at an angle, with respect to the respective first and second arms, in a plane formed by intermediate portions of the first and second arms. 
         [0037]    In Example 28, the method of any one or any combination of Examples 21-27 optionally comprises inserting into the cervical os the substantially flat first and second feet at respective distal portions of the first and second arms, such that the first and second feet are angled upward with respect to the plane formed by the intermediate portions of the first and second arms. 
         [0038]    In Example 29, the method of any one or any combination of Examples 21-28 optionally is performed such that communicating information about a cervical dilation to an external location comprises receiving the information using a longitudinal position translation correlative to a degree of pivoting of intercoupled proximal portions of the first and second arms. 
         [0039]    In Example 30, the method of any one or any combination of Examples 21-29 optionally is performed such that using a longitudinal position translation correlative to a degree of pivoting of intercoupled proximal portions of the first and second arms comprises using at least one of: a position of a rack in a rack-and-pinion; or a position of a proximal end of a member, wherein the member is constrained such that the proximal end of the member represents the degree of pivoting. 
         [0040]    This overview is intended to provide an overview of the subject matter of the present patent application. It is not intended to provide an exclusive or exhaustive explanation of the invention. The detailed description is included to provide further information about the present patent application. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0041]    In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document. 
           [0042]      FIG. 1  illustrates an isometric drawing of an example of portions of a cervical dilation meter apparatus. 
           [0043]      FIG. 2  illustrates a top view of an example of portions of the cervical dilation meter, the arms of which can be drawn together into a closed position for insertion. 
           [0044]      FIG. 3  illustrates a side view of an example of portions of the cervical dilation meter. 
           [0045]      FIG. 4  illustrates an isometric view of an example of the arms, including an example of the pivot joint. 
           [0046]      FIG. 5  illustrates a top view of the example of the arms, including an example of the pivot joint. 
           [0047]      FIG. 6  illustrates a side view of the example of the arms, including an example of the pivot joint. 
           [0048]      FIG. 7  illustrates a front view of the example of the arms, including an example of the pivot joint. 
           [0049]      FIG. 8  illustrates a front view of the example of the arms, including an example of the pivot joint. 
           [0050]      FIG. 9  illustrates an isometric view of an example of an arm and, at its proximal portion, a pivot joint. 
           [0051]      FIG. 10  is a schematic illustration of an example of a dilation meter, in which the stem can be hollow or otherwise configured to guide a rod that extends longitudinally along a length of the stem. 
           [0052]      FIG. 11  is an exploded view of an example of portions of the apparatus in which a flexible string or cable can be used (e.g., instead of the rod) to communicate the cervical dilation information from the arms to an external gauge. 
           [0053]      FIG. 12  is an exploded view of an example of portions of the apparatus in which a rack-and-pinion configuration of the pivot can be used (e.g., instead of a rod or a flexible string or cable) to communicate the cervical dilation information from the arms to an external gauge assembly. 
           [0054]      FIG. 13  is an exploded view of an example of portions of the apparatus in which a tension cable can be used to communicate a force, such as to bias the arms away from each other. 
           [0055]      FIG. 14  is an example of portions of the apparatus in which a dial gauge can be provided and coupled via a cable within a flexible sheath to a receptacle of a pivot joint from which the arms extend. 
           [0056]      FIG. 15  is a schematic diagram corresponding to an example of the apparatus such as shown in the example of  FIG. 14 . 
       
    
    
     DETAILED DESCRIPTION 
       [0057]      FIG. 1  illustrates an isometric drawing of an example of portions of a cervical dilation meter  100  apparatus. In this example, the cervical dilation meter  100  can include arms  102 A-B, which can be drawn together into a closed position, such as for insertion. In an example, the arms  102 A-B can include respective proximal portions  103 A-B, intermediate portions  104 A-B, and distal portions  105 A-B, which can be configured such as shown in the example of  FIG. 1 . 
         [0058]    In an example, the proximal portions  103 A-B can be intercoupled to each other, such as at a pivot or other moving or flexing joint  110 . The joint  110  can be configured to hold the proximal portions  103 A-B close to each other while permitting the distal portions  105 A-B to be movably spread apart from each other. This can allow measuring of an amount of cervical dilation, such as when the distal portions  105 A-B are positioned within or beyond the cervical opening, for example, such that the distance between at least one of the distal portions  105 A-B, the intermediate portions  104 A-B, or the proximal portions  103 A-B represents the amount of cervical dilation. In an example, the cervical dilation meter  100  can include a cervical dilation gauge assembly  112 , which can include a stem  114 . The stem  114  can have a length (e.g., such as about 33 centimeters) that extends from its distal portion, such as at the joint  110 , to its proximal portion, which can include or be coupled to an external gauge. The external gauge can be configured to provide a user with a visual or other external indication of the amount of cervical dilation. This external indication can be based upon cervical dilation information that is communicated along the stem  114 , such as explained below. 
         [0059]    In an example, the spreading apart of the distal portions  105 A-B of the arms  102 A-B results from providing a bias force that is communicated to the distal portions  105 A-B of the arms  102 A-B In an example, the cervical dilation meter  100  can be configured such that the bias force against the cervical or vaginal walls is enough to hold the cervical dilation meter  100  apparatus in place, with the distal portions  105 A-B in or beyond the cervical opening, such as to allow measuring of the amount of cervical dilation, but not such much as to significantly distort the dilation measurement. In an example, the cervical dilation meter  100  apparatus is held in place using the bias force and without requiring active fixation of such distal portions  105 A-B to the cervix. This means that attachment to the cervix by clipping to tissue or by penetrating tissue is not required. By not requiring active fixation, the present techniques can increase convenience and can reduce discomfort, tissue trauma, or risk of infection. Instead of using active fixation, the present techniques can provide an outward lateral force can cause the arms  102 A-B to be continuously engaged with vaginal walls or cervical walls. The lateral outward force is sufficient to overcome the inward lateral force exerted by the vaginal and cervical walls against the arms  102 A-B. Engagement of proximal portions of the arms  102 A-B with the vaginal walls, e.g., because of their shape, allows the internal portions of the cervical dilation meter  100  to be secured and retained within the body cavity, while engagement of the distal ends of the arms  102 A-B with the cervical walls allows the relative movement of the arms  102 A-B to measure cervical dilation without requiring the active fixation of invasive physical penetration, or attachment or gripping of cervical tissue (e.g., by needles, barbs, clamps, clips, grips). 
         [0060]    In an example, the bias force can be provided at least in part by a spring  118 , such as can be located about a pin of a rotational pivot joint  110 , or located elsewhere. In an illustrative example, the spring  118  can have about six coils, an inner diameter of about 0.454 inches, an outer diameter of about 0.556 inches, a body length of about 0.39 inches, a wire diameter of about 0.051 inches, and can be wound around a mandrel having a mandrel diameter of about 0.36 inches, such available from Century Spring Corp. of Los Angeles, Calif., U.S.A. or Lee Spring Co. Other spring dimensions or configurations can be used, for example, such as can have between 5.0 and 8.0 coils, an inner diameter between about 0.2 inches and about 0.4 inches, an outer diameter between about 0.25 and 0.55 inches, a body length of about 0.18 and 0.4 inches, or other suitable dimensions or configurations. 
         [0061]    However, neither a rotational pivot joint, or a spring is required. In an example, the bias force can be provided at least in part by a shape-memory property of the plastic or other material used for the arms  102 A-B, such as in an example in which the proximal ends of the arms  102 A-B can instead be joined together by a flexing joint  110 , such as in a manner like that of a tweezers or forceps. In another example, the bias force can be provide at least in part by a spring  122 , such as can be located along the stem  114 , such as at or near its proximal portion, or at or near its distal portion. In an illustrative example, the bias force can be communicated from a spring  122  at or near the proximal end of portion stem  114  to the arms  102 A-B, such as via an elongate member extending along the stem  114 . In an example, such an elongate member can include a cable or a rack (e.g., of a rack-and-pinion) or a shaft, such as explained below. 
         [0062]      FIG. 2  illustrates a top view of an example of portions of the cervical dilation meter  100 , the arms  120 A-B of which can be drawn together into a closed position for insertion. As illustrated in the example of  FIG. 2 , the bias force can be provided at least in part by the spring  118 , such as can be located about the pin  200 , such as with spring ends inserted into and retained by the respective arms  102 A-B. As can be observed by viewing the example of  FIG. 2 , the bias force holding the apparatus in place need not be confined to the distal portions  105 A-B of the arms  102 A-B pressing against the internal walls of the cervix. In the example of  FIGS. 1-2 , the intermediate portions of the arms  102 A-B can include outwardly bowed intermediate portions  104 A-B. These outward bows can be referred to as cephalic curves. In an example, the outward-facing convex sides of the outwardly bowed intermediate portions  104 A-B are shaped so that they can engage the respective opposing vaginal walls or proximal outer regions of the cervix, when inserted. This can help deliver a portion of the bias force to the respective vaginal walls or proximal outer regions of the cervix, which can help hold the cervical dilation meter  100  in place, such as while measuring the change in cervical dilation from zero (0) centimeters to ten (10) centimeters during early labor. In an example, the bowed cephalic curves of the intermediate portions  104 A-B can be sized and shaped to accommodate a descending fetal head between their opposing concave portions during birthing. In an example, the fetal head can be accommodated within the cephalic curves without dislodging the cervical dilation meter  100 , such as until the descending fetal head begins to push against the concave portions of the cephalic curves, which can then automatically dislodge the cervical dilation meter  100  without requiring any clinician or other user intervention. In another example, entry of the fetal head between the opposing concave portions of the cephalic curves during birthing automatically dislodges the cervical dilation meter  100 , without requiring any clinician or other user intervention. 
         [0063]    In an example, the cephalic curves can respectively include a chordal length  202  (directly across) of about 3.5 cm. In an example, the cephalic curves can respectively include a curved or circumferential length of about 4.75 cm. In an example, the cephalic curves are bowed out by an amount that is between about 0.5 cm and about 1.0 cm from the chordal dimension. 
         [0064]      FIG. 3  illustrates a side view of an example of portions of the cervical dilation meter  100 . In an example, the intermediate portions  104 A-B of the respective arms  102 A-B can respectively extend upward from a plane formed by the proximal portions  103 A-B of the respective arms  102 A-B, such as by an angle of about 15 degrees. This upward angle or curvature (which can be referred to as a pelvic curve) can help allow placement of the cervical dilation meter  100  even if the cervix is in a mid or anterior position. 
         [0065]    In an example, the respective distal portions  105 A-B of the respective arms  102 A-B can extend upward from a plane formed by the intermediate portions  104 A-B of the respective arms  102 A-B, such as by an angle that is about 30 degrees. This upward angle can help allow the cervical dilation meter  100  to be placed such that the respective distal portions  105 A-B of the respective arms  102 A-B can be easily positioned in the cervical canal, just above the internal cervical os, below the fetal head. 
         [0066]      FIG. 4  illustrates an isometric view,  FIG. 5  illustrates a top view,  FIG. 6  illustrates a side view,  FIG. 7  illustrates a front view, and  FIG. 8  illustrates a back view of an example of the arms  102 A-B, including an example of the pivot joint  110 , in which facing opposing-shell pivot joint housings  400 A-B can be used to carry the spring  118  and the pin  200 . In this example, one of the housings  400 A-B can be coupled to a snap-in receptacle  402 , which can extend outward from the housing  400 B, such as at an angle of about 20 degrees. A distal portion of the stem  114  can be inserted into and retained by the receptacle  402 , such as by snap-fitting the stem  114  into the angled receptacle  402 . In an example, the angled receptacle  402  can permit the inserted stem  114  to bend slightly toward the same side of the apparatus  100  as the intermediate portions  104 A-B and the distal portions  105 A-B. 
         [0067]    In an example, the respective distal portions  105 A-B can include substantially flat or other feet  404 A-B. In an example, each foot  404 A-B can provide an outward-facing surface area that can be between about 2.4 cm 2  and about 3.84 cm 2 . The feet  404 A-B can have rounded or otherwise atraumatic distal corners and edges, or can be made of (or coated by) a softer durometer material, such as to help avoid or reduce the possibility of tissue abrasion or other injury to the mother or fetus. In an example, the feet  404 A-B can be hingedly or flexibly attached to the intermediate portions  104 A-B, such as by respective flexing couplers  406 A-B. In an example, the flexing couplers  406 A-B can include portions that are thinner than the respective feet  404 A-B and thinner than the respective intermediate portions  104 A-B, such as to provide the flexing. The flexing between the feet  404 A-B and the respective intermediate portions  104 A-B can, in an example, help resist upward movement of the cervical dilation meter  100  into a lower uterine segment. Such flexing can also help accommodate downward pressing of the fetal head against the feet  128 A-B in an example. Such flexing can also help ease removal of the cervical dilation meter  100  without damaging cervical, vaginal, or other tissue during the removal. In an example, the inward facing portions of one or both of the feet  404 A-B can optionally include a pressure sensor, such as to monitor pressure of the fetal head pressing against such inward-facing portions of the feet  128 A-B. Moreover, the orientation of the flexing feet  404 A-B, in combination with the cephalic curves of the intermediate portions  104 A-B of the arms  102 A-B can help direct pressure, delivered outward by the feet  404 A-B, more laterally against the cervical walls, rather than directing such pressure upward toward the uterus. 
         [0068]      FIG. 9  illustrates an isometric view of an example of an arm  102 B and, at its proximal portion, a pivot joint  110  including a pivot joint housing  400 B including an opening  902  into which the pin  200  (of the opposing pivot joint housing  400 A at a proximal portion of an arm  102 A) can be inserted. This allows rotational pivoting about the pin  200 , which can be driven by the spring  118  carried within the housings  400 A-B, with ends of the spring  118  received into respective slots  904 A-B in the respective arms  102 A-B. In this way, the spring  118  can press against the outward sidewalls of the slots  904 A-B to impart the outward bias force to the arms  102 A-B, such as to hold the apparatus  100  in place for measuring cervical dilation. 
         [0069]    In examples such as those shown in  FIGS. 1-9 , portions of the apparatus  100 , such as the arms  102 A-B, the pivot joint  110 , the stem  114 , or other portions, can include or consist of molded polypropylene. This can provide an inexpensive apparatus  100 , such as to provide a single-use disposable apparatus  100 . In another example, brass or aluminum components can be used, such as to provide a more durable re-usable apparatus  100  that can be heat or chemically sterilized between uses. 
         [0070]      FIG. 10  is a schematic illustration of an example of a dilation meter  100 , in which the stem  114  can be hollow or otherwise configured to guide a rod  1000  or other member that extends longitudinally along a length of the stem  114 . This can permit communicating of cervical dilation information from the arms  102 A-B to an external gauge  1002 . The example of  FIG. 10  illustrates that a rotational pivot joint  110  can be omitted. Instead, the arms  102 A-B can be joined (e.g., in a wishbone-like fashion) to the distal portion of the stem  114 . A shape memory property of the arms  102 A-B and their respective attachments to the stem  114  can allow the distal portions of the arms  102 A-B to be drawn together, such as for insertion into the cervix, and to be self-spread apart, such as during the cervical dilation, such as to provide information about the degree of the cervical dilation. 
         [0071]    In the example of  FIG. 10 , a distal portion of the rod  1000  can be pivotably connected (e.g., via a pin) to proximal portions of respective resilient linkages  1004 A-B. The distal portion of the linkage  1004 A can be pivotably connected to the arm  102 A, such as via a pin at a proximal portion  103 A (as shown) or to a more distal portion of the arm  102 A. The distal portion of the linkage  1004 B can be similarly pivotably connected to the arm  102 B, such as via a pin at a proximal portion  103 B (as shown) or to a more distal portion of the arm  102 B. In this way, as the arms  102 A-B spread apart from each other, a proximal portion of the rod  1000  is drawn into a proximal portion of the tubular or other stem  114  and, concurrently, a distal portion of the rod  1000  is extended out from a distal portion of the tubular or other stem  114 . 
         [0072]    In an example, the external gauge  1002  can include cervical dilation markings  1006  on the rod  1000 , which can be read against the end of the tubular or other stem  114  to provide an external indication of the degree of cervical dilation to a viewing user. For example, the rod  1000  can be manufactured such that the markings  1006  provide a scale that corresponds to the number of centimeters of cervical dilation measured using the arms  102 A-B. The scale can be linear, but need not be linear. In an example, there can be a logarithmic correlation between the scale of the markings  1006  on the rod  1000  and the degree of separation of the arms  102 A-B, which provides the indication of cervical dilation. 
         [0073]      FIG. 11  is an exploded view of an example of portions of the apparatus  100  in which a flexible string or cable  1100  can be used (e.g., instead of the rod  1000 ) to communicate the cervical dilation information from the arms  102 A-B to an external gauge  1102 . A distal end of the cable  1100  can be anchored or otherwise affixed at one of the arms  102 A-B, such as at a proximal portion  103 A-B or an intermediate portion  104 A-B of the one of the arms  102 A-B. Measurement of the indication of cervical dilation at a location that is near the proximal portions  103 A-B of the arms can help avoid entanglement or obstruction of the cable  1100  by the fetal head or other instrumentation that may be inserted into a vagina, cervix or uterus. In an example, the cable anchoring or affixing can involve tying off or otherwise widening a distal end of the cable  1100  and inserting the cable  1100  through a hole  1101 B in the one of the arms  102 A-B, such that the widened end of the cable  1100  cannot be pulled through the hole  1101 B in the one of the arms  102 A-B. The cable  1100  can then extend across to the other one of the arms  102 A-B, such as through an opposing hole  1101 A in the other one of the arms  102 A-B. The cable  1100  can then extend within or along a tubular lumen, sheath, or other cable guide along that other one of the arms  102 A-B, into or along the pivot joint housing  400 A-B, within or along the receptacle  402 , within or along the stem  114 , and to the external gauge assembly  1102 . 
         [0074]    At the external gauge assembly  1102 , the cable  1100  can terminate at a gauge plunger  1106 , which can travel back-and-forth within a transparent cylindrical or other elongate gauge body  1108 , as the arms  102 A-B are drawn toward each other or spread apart from each other. Scale markings on the gauge body  1108  can be read against the gauge plunger  1106  to provide an external indication of cervical dilation. Tension in the cable  1100  can be maintained by a compression spring  1110 , which can be located around the cable  1100 , such as at or near the proximal end of the cable  1100 . The compression spring  1110  can be used in addition to the spring  118 , in an example, or instead of the spring  118 , in another example. The cable-tensioning compression spring  1110  can have its proximal end seated against the plunger  1106  and its distal end seated against a stop  1112  portion of the stem  114 . In an example, a distal portion of the gauge body  1108  can also be seated against the stop  1112 . In an example (not shown in  FIG. 11 ), the compression spring  1110  can instead be located near the pivot  110 , for example, its force can be communicated to the external gauge assembly by a rod or tube within the stem  114 . 
         [0075]    The exploded view example of  FIG. 11  also demonstrates an example in which the pivot  110  can include a disk-like base portion  1114 , coupled to the receptacle  402 , and including the pin  200 . The pivot  110  can also include a proximal end of the arm  102 B, which can include a housing  400 B that includes disk  1118  having a center hole  1116  through which the pin  200  can be inserted. Next, the spring  118  can then be placed about the pin  200 , such as with one end of the spring  118  inserted into or otherwise constrained by the arm  102 B, and the other end of the spring  118  then inserted into or otherwise constrained by the arm  102 A. Next, the proximal end of the arm  102 A, which can include a cylindrical housing to carry the spring  118  and a center hole  1120 , can be placed with the center hole  1120  about the pin  200 , with the end of the spring  118  constrained by the arm  102 A, such as explained above. Then, a snap-on cap  1122  can be placed about and snapped onto the pin  200 , which can help hold the various components of the pivot  110  together. 
         [0076]      FIG. 12  is an exploded view of an example of portions of the apparatus  100  in which a rack-and-pinion configuration of the pivot  110  can be used (e.g., instead of a rod  1000  or a flexible string or cable  1100 ) to communicate the cervical dilation information from the arms  102 A-B to an external gauge assembly  1202 . In this example, the pivot  110  can include a pinion pivot base  1204 . The stem receptacle  402  can extend outward from the pivot base  1204 , in a similar manner to that described above. The base  1204  can include separate pins  200 A-B that can extend upward into respective receptacles  1206 A-B of respective arms  102 A-B. This can allow the respective arms  102 A-B to pivot about their respective pins  200 A-B. This can allow the arms  102 A-B to be drawn toward each other or spread apart from each other. The pivoting proximal ends of the arms  102 A-B can include opposing facing pinion toothed gears  1208 A-B. A toothed geared distal portion of a rack  1210  can be inserted between the opposing facing pinion toothed gears  1208 A-B. Like the rod  1000 , the rack  1210  can extend proximally through the tubular stem  114  to an external gauge assembly  1202 . In an example, a distal portion of the rack  1210  can travel into a rack receptacle  1212 . A proximal end of the rack  1210  can include a plunger  1214  that travels within an at least partially transparent barrel  1216 . The barrel can include markings  1218  forming a cervical dilation scale for user readout. In this way, as the cervix dilates, and the distal portions of the arms  102 A-B spread apart, a distal end of the rack  1210  travels toward or into the receptacle  1212 , and a proximal end of the rack  1210  travels such that the rack plunger  1214  moves more distally within the barrel  1216  of the dilation gauge assembly  1202 . The barrel  1216  can include an end-cap  1220  at its proximal end. A spring  1222  can be located near the proximal or distal portion of the rack  1210 , such as at the barrel  1216  or at the receptacle  1212 . The spring  1222  can be used to bias the rack  1210  in a distal direction such that the arms  102 A-B tend to self-spread apart, such as to allow measurement of the cervical dilation. The spring  1222  can be designed to provide a pushing or pulling force, as appropriate, to provide such a bias force to tend to spread the arms  102 A-B apart. A cap  1224  can be snap-fitted onto the pins  200 A-B, such as to hold or house the components of the rack-and-pinion pivot  110 . 
         [0077]    In an example, the apparatus  100  can be packaged together in a kit with an introducer that can hold the arms  102 A-B together during insertion. In an example, the introducer can include a peel-away sheath that keeps the arms  102 A-B together during insertion, but which can include two separate proximal tails that can be used to concurrently pull apart and retract the sheath, leaving the arms  102 A-B in place in the opening of the cervix, and thereby permitting such arms  102 A-B to self-expand apart from each other to measure the cervical dilation. In another example, the apparatus  100  can be provided with a proximal push-rod such as to communicate a force to hold the arms  102 A-B together during insertion. 
         [0078]      FIG. 13  is an exploded view of an example of portions of the apparatus  100  in which a tension cable  1300  can be used to communicate a force, such as to bias the arms  102 A-B away from each other. In an example, the tension cable  1300  can include a bifurcated distal portion  1302 A-B. The distal portion  1302 A can terminate at a coupling feature such as a post  1304 A, which can extend perpendicular to the distal portion  1302 A. The distal portion  1302 B can terminate at a coupling feature such as a post  1304 B, which can extend perpendicular to the distal portion  1302 B. 
         [0079]    In the example of  FIG. 13 , proximal ends of the arms  102 A-B can be coupled together, such as at a pivot joint  110 , which can include respective disks  1306 A-B at the respective proximal ends of the arms  102 A-B. The disks  1306 A-B can include respective center holes  1120 ,  1118  through which a pin  200  can be inserted. A distal end of the pin  200  can be snap fitted into or otherwise engaged to a cap  1308 , thereby holding together the cap  1308 , the disks  1306 A-B, the pin  200  and the disk  1114 , such as to provide the joint  110 . 
         [0080]    In the example of  FIG. 13 , the disks  1306 A-B can include arc-shaped, semicircular, or similar guide rails  1310 A-B. The cable distal portions  1302 A-B can respectively wrap around the outsides of the respective rails  1310 A-B. The posts  1304 A-B can be respectively inserted into and engage the respective recesses  1312 A-B. The cable  1300  can pass through a tubular receptacle  402  and a flexible tubular or other sheath  1314  back to a proximal gauge  1316 , which can be located external to the patient when the distal portions of the arms  102 A-B are located within the cervix, such as to measure its diameter. 
         [0081]    In an example, the gauge  1316  can include a proximal end of the sheath  1314 , which can include an outward flange  1315 , which can serve as a distal stop for a spring  1316 . An outward flange  1318  near a proximal end of the cable  1300  can serve as a proximal stop for the spring  1316 . In such an example, the spring  1315  can be captured between the flanges  1315  and  1318 . In an example, the spring  1315  can provide the force that is communicated by the cable  1300  to the arms  102 A-B such as to bias the arms  102 A-B away from each other during the cervical dilation measurement. In an example, a gauge pointer  1320  is optionally coupled to the flange  1318  at the proximal end of the cable  1300 , such as for reading the cervical dilation against graduations or demarcations on a transparent or translucent gauge cylinder  1322 . In another example, the flange  1318  can itself optionally be used to provide a gauge pointer for reading against the graduations or demarcations on the gauge cylinder  1322 . In another example, the apparatus  100  can be provided with a proximal push-rod (e.g., extending further proximally from the gauge pointer  1320 ) such as to communicate a force to hold the arms  102 A-B together during insertion. A dial or other gauge readout can be substituted for the linear translational gauge cylinder in this example or in one or more of the other examples described herein. 
         [0082]      FIG. 14  is an example of portions of the apparatus  100  in which a dial gauge  1400  can be provided and coupled via a cable within a flexible sheath to a receptacle  1404  of a pivot joint  110  from which the arms  102 A-B extend. The dial gauge  1400  can include a dial gauge housing  1406  having a window  1408  through which a dilation reading on a rotating dial can be read. 
         [0083]      FIG. 15  is a schematic diagram corresponding to an example of the apparatus  100  such as shown in the example of  FIG. 14 . In this example a short cable  1500  can include ends with respective couplers, such as balls  1502 A-B, that can be coupled to respective arms  102 A-B, such as by being inserted into respective sockets in the respective arms  102 A-B at a desired proximal, intermediate, or distal location along the length of such arms  102 A-B. A middle region of the cable  1500  can be coupled to a distal end of a longer cable  1504 , which can be passed through a flexible tubular or other sheath  1506 . In an example, the sheath  1506  can extend from the receptacle  1404  on the pivot joint  110  to a spring housing  1508 . In an example, the spring housing  1508  can extend outward from the dial gauge housing  1406 . A proximal end of the cable  1504  can be coupled to a distal portion of a rack gear  1510 , which can form a rack-and-pinion arrangement with a pinion gear  1512 . The pinion gear  1512  can engage a dial gear  1514 , which drives a rotational movement of a dial  1516 . The dial  1516  can provide numerical or other indicia indicative of cervical dilation, such as can be viewable through the window  1408  on the housing  1406  of the dial gauge  1400 . In an example, the pinion gear  1512  can include a multiple stage pinion gear, such as a two-stage pinion gear, such as to translate linear movement of the rack gear  1510  into a desired degree of rotation of the dial  1516 . For example, the two-stage pinion gear  1512  can include a smaller gear  1512 A, which engages the rack gear  1510 , and which rotates together with a larger gear  1512 B, which engages the dial gear  1514 . In this example, the spring housing  1508  can include a coil spring  1518 , which can be located about the cable  1504  and confined within the spring housing  1508  between the spring housing  1508  and the distal portion of the rack gear  1510 . The spring  1518  can provide a force against the rack gear  1510 . The rack gear  1510  can communicate this force via the cables  1504  and  1502  to the arms  102 A-B such as to bias the arms  102 A-B away from each other, such as for performing the cervical dilation measurement. 
         [0084]    Additional Notes 
         [0085]    The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” Such examples can include elements in addition to those shown and described. However, the present inventors also contemplate examples in which only those elements shown and described are provided. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also examples using any combination or permutation of those elements shown or described, either with respect to a particular example, or with respect to other examples shown or described herein. 
         [0086]    All publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference(s) should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls. 
         [0087]    In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. 
         [0088]    Method examples described herein can be machine or computer-implemented at least in part. Some examples can include a computer-readable medium or machine-readable medium encoded with instructions operable to configure an electronic device to perform methods as described in the above examples. An implementation of such methods can include code, such as microcode, assembly language code, a higher-level language code, or the like. Such code can include computer readable instructions for performing various methods. The code may form portions of computer program products. Further, the code may be tangibly stored on one or more volatile or non-volatile computer-readable media during execution or at other times. These computer-readable media may include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memories (RAMs), read only memories (ROMs), and the like. 
         [0089]    The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to comply with 37 C.F.R. §1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.