US3587591A

US3587591A - Obstetrical instrument for rupturing the amniotic sac

Info

Publication number: US3587591A
Application number: US774888A
Authority: US
Inventors: Raymond D Satterwhite
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-11-12
Filing date: 1968-11-12
Publication date: 1971-06-28
Anticipated expiration: 1988-06-28

Abstract

AN OBSTERTRICAL INSTRUMENT FORMED INTEGRAL WITH A FINGER OF A SURGICAL GLOVE INCLUDING A FLEXIBLE SHEATH ALONG THE BACK SURFACE OF A FINGER OF THE GLOVE, A MOVABLE FLEXIBLE BLADE ENCLOSED IN THE SHEATH AND EXTENDABLE BY A BUTTON PROJECTING THROUGH A SLOT ALONG THE TOP FACE OF THE SHEATH ENGAGEABLE BY THE PALM SIDE OF AN ADJACENT FINGER, THE BLADE HAVING AN EXPOSED POINT WHEN EXTENDED FOR RUPTURING THE AMNIOTIC MEMBRANE OF A PREGNANT WOMAN TO RELEASE THE AMNIOTIC FLUID PREPARATORY TO DELIVERY OF THE BABY.

Description

United States Patent 1 1 3,587,591

[72] 1nven10r Raymond D. Salterwhite 2,668,536 2/1954 Farries et a1. 128/305 5182 Ollie, Fort Worth, Tex. 76119 2,811,969 11/1957 Shubert 128/303 [2]] Appl. No. 774,888 2,847,012 8/1958 Eastman.. 128/303 [22] Filed Nov. 12,1968 3,126,890 3/1964 Deming 128/361 [45] Patented June 28,197] 3,362,408 1/1968 Stocki et a1.. 128/314 3,410,269 11/1968 Hovick 128/361 54 OBSTETRICAL INSTUMENT r011 RUPTURING Dalton TruluCk THE AMMOTIC SAC AtI0meyH. Mathews Garland 13 Claims, 9 Drawing Figs.

110/2981 128/329 ABSTRACT: An obstetrical instrument formed integral with a [51] Int. Cl A611) 17/42 finger of a Surgical glove including a flexible Sheath along the [50] Fleld 01' Search 128/303, back Surface ofa finger of the glove, a movable flexible blade 305, 307, 314, 315, 329, 361; 30/298; enclosed in the sheath and extendable by a button projecting 2/(Inqu" ed) through a slot along the top face of the sheath engageable by the palm side of an adjacent finger, the blade having an ex- [56] References (med posed point when extended for rupturing the amniotic mem- UNITED STATES PATENTS brane of a pregnant woman to release the amniotic fluid 1,512,943 10/1924 Martineau 30/298X preparatory to delivery of the baby.

I'II'II I PATENIEU JUN28 I971 SHEET 1 UF 2 Fig.4

Fig.|

INVENTOR. Raymond D SoHerwhHe m ue ATTORNEY OBSTETRICAL INSTUMENT FOR RUPTURING THE AMNIOTIC SAC This invention relates to obstetrical instruments and more particularly to an obstetrical instrument for rupturing the amniotic membrane at the internal opening of the cervix to release the amniotic fluid surrounding a baby in the uterus of a woman preparatory to delivery of the baby.

The amniotic membrane or sac encloses the embryo and the fetus, as the infant is known after the second month, which is cushioned in a fluid environment provided by the amniotic fluid contained within the sac. As the fetus grows and the sac enlarges the quantity of amniotic fluid increases to provide cushioning or protection for the enlarging infant. The amount of the amniotic fluid surrounding the baby may be sufficient that when labor begins the muscles contracting to expel the baby from the uterus are ineffective because of the volume of amniotic fluid which is absorbing the energy and precluding expulsion of the baby. The baby may be merely moved around within the uterus thereby delaying the birth. Amniotomy or rupture of the amniotic membrane is a well known old and effective way of inducing labor, or if labor has started, it may render more effective the muscular contractions of labor when they are advanced enough to produce delivery. Under any circumstances it is generally preferred that the rupture be followed by delivery of the baby within a reasonable period of time, such as within about 24 hours, in order to minimize the hazard of infection to the mother and baby. When the membrane is so ruptured labor often may follow with subsequent birth within 1 or 2 hours.

One method of rupturing the amniotic membrane commonly used has included the use of the Allis clamp which is not specifically designed for this technique or type of operation and which not only requires the insertion of two fingers of one hand of the operating physician into the vagina and cervical canal but additionally requires the insertion of the Allis clamp which must be manipulated by the other or external hand of the physician. The Allis clamp method thus requires both hands of the physician and substantial dilation of the cervical opening. Other methods of performing the operation include using an extensible cutter supported along the palm side of one finger of the physician and operable by a flexible rod extending to an indicator member positioned along the wrist of the physician with the rod being bent by flexing the wrist and the indicator showing the position of the cutter element. The instrument is fairly easily displaced on the physician's fingers and also requires the extension of a portion of the instrument outwardly of the cervical canal and the vagina. A still further approach to rupturing of the sac has included a finger piece or portion of a surgical glove having an exposed puncturing point formed thereon and requiring that the supporting finger be held against one side of the vagina and cervical canal away from the exposed point to prevent tearing of the tissue during the insertion and positioning of the finger to properly rupture the sac. Thus, in general the prior art has either included mechanism requiring undue protection against tearing of the tissue, the use of two hands, or structure which somewhat limits the ability of the examining and rupturing finger to freely move within the area of the portion of the sac to be punctured.

It is, therefore, an object of the invention to provide an obstetrical instrument particularly adapted to the rupture of the amniotic sac or membrane for release of amniotic fluid from the uterus preliminary to delivery ofa baby.

It is another object ofthe invention to provide an obstetrical instrument of the character described which is insertable through the vagina and connecting cervical canal to the opening of the cervical canal into the uterus where the instrument is activated to rupturethe portion of the amniotic sac covering the opening of the cervical canal into the uterus.

It is a further object of the invention to provide an obstetrical instrument of the character described which is accommodated to the finger of the operating physician by formation of the instrument integral with a surgical glove finger such that substantial flexibility of the operating finger is maintained to permit manipulation of the finger to the rupturing the membrane. v

It is a particularly important object of the invention to provide an obstetrical instrument of the character described which has smooth contoured surfaces permitting insertion along the'vaginal and cervical canals to the point of membrane rupture without tearing or unnecessarily irritating the tissue defining each canal thus providing maximum protection to such tissue without holding the operating finger in any special position or along any one surface of either canal during insertron.

It is another object of the invention to provide an obstetrical instrument of the character described including an extendable cutting point held at a retracted protected position until the operating finger is at a rupturing position along the membrane and is then extended to a rupturing position.

lt is still a further object of the invention to provide an obstetrical instrument of the character described which includes a blade movable from a protected retracted position to extended rupturing position by an adjacent finger of the operating physician when the operating finger is within the cervical canal.

It is another object of the invention to provide an obstetrical instrument of the character described having a cutting blade point aligned at an angle which permits withdrawal of the operating finger without engaging and tearing tissue defining the cervical and vaginal canals.

It is a further object of the invention to provide an obstetrical instrument of the character described having a cutting blade extendable and lockable at operating position by a single movement of an adjacent finger of the physician. v

It is another object of the invention to provide an obstetrical instrument of the character described which may be economically constructed of sterilizable materials so that the surgical glove including the integral instrument is expendable and thus may be used for only a single operation and discarded.

it is a still further object of the invention to provide an obstetrical instrument as described including a flexible sheath formed along the back side of one finger of a surgical glove, and a knife enclosed within the sheath and movable from a retracted to an extended position at which a membrane piercing point on the knife projects through an opening in the sheath disposed along the tip end of the finger of the glove.

It is another object of the invention to provide an obstetrical instrument of the character described in which the finger of the surgical glove carrying the instrument is reinforced while retaining its flexible character and is sufficiently thin that the sensitivity of the operating finger of the physician within the glove finger is essentially retained.

It is still a further object of the invention to provide an obstetrical instrument of the character described having a membrane rupturing point of limited length so that the amniotic sac may be ruptured while minimizing possibility of damage to the baby.

It is another object of the invention to provide an obstetrical instrument as described wherein the knife blade is locked against retraction once moved to its extended position.

Additional objects and advantages of the invention will be readily apparent from reading the following description of the device constructed in accordance with the invention and by reference to the accompanying drawings thereof wherein:

FIG. 1 is a view in perspective of a surgical glove including an obstetrical instrument constructed in accordance with the invention secured along one finger of the glove;

FIG. 2 is an enlarged fragmentary top view of the instrument and a portion of its supporting surgical glove finger with the blade at its retracted position;

FIG. 3 is a side view in section along the line 3-3 of FIG. 2;

FIG. 4 is a transverse view in section along the line 4-4 of FIG. 3;

FIG. 5 is a view in section a similar to FIG. 3 with the blade proper position for extended to expose the point at membrane-rupturing position;

FIG. 7 is an enlarged fragmentary top plan view of a portion of the blade of FIG. 6 showing the membrane rupturing points of the blade;

FIG. 8 is a sectional view of the female human anatomy carrying a child during pregnancy with the operating finger of the physician carrying the obstetrical instrument inserted into the cervical canal; and

FIG. 9 is a view in section similar to FIG. 8 with the membrane-piercing point of the instrument blade extended and piercing the membrane covering the opening of the cervix into the uterus. Referring to the drawings, an obstetrical instrument embodying the invention is disposed along the back or top and end surface of a finger 21 of a surgical glove 22 formed of a thin latex rubber or plastic film which may be of a throwaway or disposable type. Such gloves are well known and serve to minimize infection danger by fully covering the hand of the operating physician while preserving the sensitivity of the fingers to touch. The instrument is preferably formed integral with the glove finger ofa material compatible with the material forming the glove.

The instrument 20 includes a sheath or housing 23 contoured substantially to the shape of the glove finger 21 when fitted on the finger 24 of an operating physician as illustrated in FIG. 3 so that in use it will conform as closely as possible to the shape of the physician's operating finger 24. The sheath 23 is disposed along the back surface 25 and an upper portion of the tip surface of the glove finger. The sheath is provided with an internal longitudinal recess 31 extending along the back face of the glove finger 21 and opening downwardly and outwardly through a slot 32 across the tip end of the glove finger. A locking cleat 33 is formed with the sheath projecting downwardly into the recess 31 as seen in FIG. 3. The front face 33a of the locking cleat is formed at an acute angle with the top surface of the recess 31. A substantially rectangular slot 34 extends along the top of the sheath opening into the recess 31. The back end portion 23a of the sheath 23 is thickened behind the recess 31 and gradually decreases in thickness and is arcuate in shape as viewed in plan in FIG. 2 so that its top surface blends into the back face of the glove finger 21 to provide a smooth continuous surface connection between the sheath and the glove finger surfaces so that the glove finger with the obstetrical instrument will slide smoothly without tissue damage or irritation through the vaginal and cervical canals during insertion to operating position. Laterally, as viewed in FIG. 4, the sheath 23 is gradually reduced in thickness as it extends downwardly and integrally joins a skirt or envelope 35 of relatively thin material fully encasing the glove finger along its side, palm and tip surfaces as evident in FIGS. 3-and 4. The envelope 35 is formed as thin as practicable to reinforce the portion of the glove finger 21 supporting the sheath 23 while increasing the total thickness of the combined glove finger and envelope a minimum-to retain the sensitivity of the sense of feel of the physician's finger within the glove finger. Also, it is preferred that maximum mobility or flexibility ofv the physician's finger be retained consistent with structural strength of the glove along the finger portion 21 supporting the instrument 20.

A blade 40 having a membrane puncturing tip portion 41 bifurcated to provide dual points 42 is slidably disposed in the recess 31 of the sheath 23. The blade is slightly narrower tan the width of the recess 31, FIG. 4, and slightly shorter than the length of the recess, FIG. 3, so that at its fully retracted position it is fully encased within the recess. The relatively small tolerance between the width of the blade and the width of the recess insures substantially straight movement of the blade from its retracted to its extended position and holds the blade substantially rigid laterally at its extended operating position. An operating handle and lock 43 is secured on the top face of the blade for engagement by a finger of the operating physician to move the blade from its retracted position of FIG. 3 to its extended position of FIG. 5 and to lock the blade at such extended position. The handle 43 is notched at 44 providing the blade makes an acute angle with the top face 51' of the blade corresponding substantially to the angle of the face. 33 on the locking cleat 32 for locking the blade at its extended position. The top face of the handle 43 is serrated or roughed as at 46 to facilitate engagement by the physician's finger for moving the blade from its retracted to its extended position.

Between the dual tips 42 the blade is provided with an arcuate concave end recess 42a of a depth as measured from a line between the dual tips substantially the thickness of the average amniotic membrane to provide a safety factor rending to limit the penetration of the tip into the membrane to minimize possibilities of damage to the baby. The blade is inherently bent as to the curvature shown in FIG. 6 such that a major portion of its bottom face 400 is convex while its top face 40b is generally concave when relaxed. When the blade is extended it is then distorted to the shape shown in FIG. 5 so that it binds somewhat as it passes through the slot 32 holding it more tightly in place at its rupturing position. A further element of control of the depth to which the points may penetrate a membrane is provided by the extent of projection of the rupturing tips beyond the end or tip of the envelope 35 as seen in FIG. 5. The curvature of the end portion of the blade along with the angle ofthe opening of the slot 32 and the overhang of the thickened top end portion of the sheath 23 above the slot 32 relative to the tip portion of the envelope 35 combine to control the extent to which the blade tips are generally inserted into or penetrate the membrane along with, of course, the technique of the operating physician.

The sheath 23 and the envelope 35 are formed of latex rubber or plastic material having sufficient rigidity to properly house and hold the blade 40 while being as flexible as possible to provide maximum mobility to the operating finger 24 of the physician inserted into the glove finger 21 when the instrument is in use. Also, the material forming the sheath and envelope must be readily securable to the surgical glove finger so that the glove finger, instrument sheath, and envelope function essentially as one during operation ofthe instrument.

The blade 40 and the handle 43 also may be formed of a plastic which, however, must have sufficient rigidity to permit it be sharpened at the points 42 to the extent required for readily rupturing the amniotic membrane.

The operation of the obstetrical instrument 20 is illustrated in FIGS. 8 and 9 showing a section of a pregnant woman in a reclining position at which delivery is normally accomplished. When the physician has determined that the patient has arrived at the proper stage the instrument may be used to rupture the amniotic membrane 55 along the membrane portion 55a over the opening 56 from the cervix 57 to the uterus 58. The physician's hand covered by the surgical glove with the obstetrical instrument is inserted into the vagina 60 of the patient with the palm side of the hand facing the top 6011 of the vagina or forward with respect to the patient and the back side of the hand extending along the bottom 60b of the vagina. The finger carrying the instrument is advanced along the vagina to the cervical canal with the distal portion of the finger being bent somewhat for entry into the cervical canal and further penetration to the entrance 56 of the canal into the uterus. A particularly important feature of the instrument is that during the insertion through the vagina and the cervical canal the smooth contours of the surfaces of the instrument and the retracted position of the blade minimize any tearing or irritation of the surrounding tissue and does not require special positioning of the finger to avoid tissue damage. As the physicians finger moves along the vagina it reaches the external opening 61 of the cervical canal 62 where the finger is advanced upwardly through the canal toward the uterus. As the operating finger advances in the cervix the hand and the finger positioned with the palm side of the finger upwardly in the cervix so that when the opening 56 of the cervix into the uterus is reached the thinner portion of the envelope 35 of the instrument spaced toward the palm side of the finger 21 from the knife opening 32 reaches the membrane portion 55a so that the physician can feel the membrane with the tip .of his finger 24. The operating finger may be used to carefully partially strip back the amniotic membrane from the uterine attachment and allow an accumulation 62a of the amniotic fluid 62 along the top of the head of the baby along the portion 55a of the membrane. This provides more fluid protection and further spaces the membrane from the head of the baby during the rupture step.

When the physician has determined that he has made the proper contact with the membrane 55 and has prepared the membrane by finger manipulation for rupturing to the extent desired, the blade 40 is extended for the membrane rupturing step. The operating finger is in the position in the cervix at the membrane as shown-in FIG. 8. The index finger 24a of the physician is moved laterally into overlapping relationship with the operating finger with the palm side of the distal portion of the index finger engaging the surface 46 of the handle 43. The index finger is straightened toward the end of the operating finger advancing the blade 40 in its recess 31 toward the tip of the operating finger extending the top portion of the blade through the opening 32 in the sheath 23 to the fully exposed position of H68. 5 and 9. As the blade is extended through the slot it is bent downwardly as viewed in FIG. 5. When the back edge face 50 of the blade passes the locking cleat 32 the bending stress in the blade causes the back end portion of the blade to spring upwardly into the notch defined at the front face 33a of the cleat 33. The angle of the back edge 50 of the blade and the front face 33a of the cleat correspond so that the face 50 seats against the cleat face 33a to lock the blade against retraction. Also, the upward springing of the blade moves the handle 43 to the position of FIG. 5 at which the flange portion 45 overlaps the top surface of the sheath 23 toward the free end of the instrument locking the blade against the flexing inwardly so that the blade cannot be moved to disengage its back face 50 from the locking cleat face 33a. The tips 42 project outwardly from the opening 32 in the sheath and divurgently with respect to the end surface of the envelope 35. The operating finger 24 is then gently bent toward its palm side, upwardly in terms of FIG. 9, and drawn along the membrane portion 55a causing rupturing of the membrane covering the opening of the cervix into the uterus. The extent of movement required by the operating finger, the exact angle of the blade tip with the membrane, and other factors involved in effecting the membrane rupture will, of course, vary with patients and are within the control and judgement of the physician. When he has determined that the membrane is properly ruptured by the draining of the amniotic fluid from the uterus through the cervix and the vaginal canal, the obstetrical instrument is removed by gently withdrawing the hand of the physician until it has been completely removed from the patient. Since the rupturing blade is locked at its extended position, some care must be exercised during the withdrawal step not to damage the tissues around the cervical and vaginal canals. As evident from the view of FIG. 9 this may be carried out by gently pressing the operating finger towards it back side or in other words, downwardly along the bottom or back surface 57a of the cervical canal and 60b of the vaginal canal. Such movement of the operating finger will maintain it spaced from the opposite or top sides of the cervix and vagina and the sloping or convergence of the end portion of the blade toward the palm side of the distal portion of the operating finger insures against contact of the tips 42 with the tissue of the cervix and vagina. After the physicians hand is removed and the membrane is known to be properly ruptured, the surgical glove with the instrument may be removed and disposed of.

It will be evident from the description of the operation of the instrument that it is preferred that the envelope 35 be as thin as practicable consistent with proper securing of the instrument on the surgical glove finger so that maximum sensitivity of the palm surface of the physicians finger may be retained and also that the envelope and finger portion of the glove be as tight as practicable on the finger of the physician to enhance its sensitivity to aid in his'ability to determined the proper location and conditions for rupture of the membrane.

The instrument 20 has been illustrated and described on the second finger next to the index finger though it is to be understood that the instrument may be formed on any desired finger of a surgical glove for use on either hand ofa physician. The exact shape of the blade tips 42, their spacing. and the depth of the end recess 42a are varied as required. The blade also may be made with a single piercing point. Also, the angle of divergence of the extended blade end portion 41 with the adjacent surface of the end of the envelope 35 may be varied to satisfy different membrane thickness and membrane cervical canal angle conditions. Where the material forming the blade 40 is sufficiently stiff the blade may remain at its extended locked position as in FIG. 5 without the need for the locking flange 45 on the handle 43 and thus under such conditions the flange may be dispensed with. Care must be exercised in forming the ribbed surface 46 that it is easily engaged by a finger to extend the blade but is not so rough that tissue will be irritated or torn by contact with it.

It will now be seen that a new and improved obstetrical tool for rupture of the amniotic membrane in a pregnant woman preliminary to delivery of her child has been described and illustrated. It will be seen that the instrument includes an extendable blade which is enclosed as a fully retracted position during insertion of the physicians operating finger and hand to membrane rupturing position thereby minimizing tissue damage along the surfaces of both the vagina and the cervix. it will be further seen that the instrument is tightly secured on the operating finger of the surgeon maintaining the sensitivity of the finger through the palm side of the surgical glove finger supporting the instrument. It will also be recognized that the integral instrument glove unit may be economically manufactured and subsequently disposed of after use.

The foregoing description of the invention is explanatory. only and changes in the details of the construction illustrated may be made by those skilled in the art within the scope of the appended claims without departing from the spirit of the invention.

What is claimed and desired to be secured by Letters Patent is:

lclaim: 1

1. An obstetrical instrument for rupturing an amniotic membrane for release of amniotic fluid within the membrane to facilitate the birth of a baby contained therein, said instrument comprising: a sheath adapted to be secured along the back of a finger; a blade supported in said sheath for axial movement between a retracted fully incased position within said sheath and an extended locked position at which a free end portion of said blade projects from said sheath along an end of said finger for rupturing said amniotic membrane by manipulation of said finger, an operator member connected with said blade and engageable by an adjacent finger on the hand of an operator supporting said instrument for moving said blade from said retracted to said extended position responsive to movement of said adjacent finger only; said blade and said sheath being operatively interrelated whereby said blade resists extension from said retracted position and is positionable in said extended position by said adjacent finger only and locking means within said sheath and on said blade operator member cooperating together to lock said blade at said extended position, said operator member including a locking flange coacting with a surface of said sheath for locking said blade.

2. An obstetrical instrument as defined in claim 1 wherein said sheath is secured along a finger piece adapted to fit said finger.

3. An obstetrical instrument as defined in claim 2 wherein said finger piece is one finger ofa surgical glove.

4. An obstetrical instrument as defined in claim 3 including a reinforcing envelope connected with said sheath over said finger of said glove for holding said instrument along said glove finger..

5. An obstetrical instrument as defined in claim 4 wherein said sheath and said envelope are fused with said glove finger whereby said sheath and said envelope are substantially integral with said glove finger.

6. An obstetrical instrument as defined in claim wherein said sheath, said envelope, and said blade comprise flexible material permitting mobility of said finger within the surgical glove finger in said envelope and sheath.

7. An obstetrical instrument as defined in claim 6 wherein said operator member comprises a handle on said blade projecting through said sheath for moving said blade from the retracted to the extended position.

8. An obstetrical instrument for rupturing an amniotic membrane for release ofamniotic fluid within the membrane to facilitate birth of a baby contained therein, said instrument comprising: a sheath having contoured internal and external surfaces adapted to conform substantially to the shape of the top, upper side, and end surface portions of a finger'supporting said instrument, said sheath extending substantially from the second joint of said finger along the top surface thereof around upper free end surface portions of said finger; a reinforcing envelope secured with said sheath and adapted to conform to the side, bottom, and end portions of said finger, said envelope connecting with said sheath along upper side and end edges; said sheath and said envelope being secured on a finger of a surgical glove with said sheath extending along the back and upper end surface portions of said glove finger; said sheath being provided with an internal recess closed at an end near said second joint of said finger extending longitudinally along the back surface of said supporting glove finger and opening at the free end of said glove finger through a transverse slot provided in said sheath at said end of said glove finger; said sheath having a longitudinally extending slot communicating through the upper surface thereof into said recess within said sheath; a locking cleat formed within said sheath projecting into said recess in said sheath between said closed end and said slot opening through the top surface of said sheath into said recess; a blade longitudinally disposed within saidrecess of said sheath for movement between a retracted position at which said blade is fully encased within said sheath and an extended position at which an end portion of said blade projects from said recess of said sheath through said slot at the free end of said sheath; means providing a point on said blade at the end portion of said blade extendable from said sheath for engaging and rupturing said amniotic membrane when said blade is at said extended position; an operating handle on said blade projecting through said slot in the top of said sheath for moving said blade from its fully encased retracted position to said extended position, the distance said handle is movable in said slot of said sheath determining the length of the stroke of said blade between said retracted and said extended positions; and said blade being shaped to direct the pointed end portion of said blade through said slot along the free end of said glove finger and flexing the inward end of said blade upwardly toward said locking cleat whereby when said blade is fully extended the inward end of said blade engages said cleat for locking said blade at said extended position. v

9. An obstetrical instrument as defined in claim 8 wherein said projecting end portion of said blade when extended is disposed at an acute angle with the end surface portion of said envelope disposed over the end of said glove finger whereby movement of said glove finger in the direction of the palm side of a finger therein engages said point on said blade with said amniotic membrane.

10. An obstetrical instrument as defined in claim 8 wherein said blade is provided with a bifurcated end having dual membrane puncturing points spaced on opposite sides of an arcuate recess having a depth substantially defining the extent of penetration of said points into a membrane punctured by said blade points.

11. An obstetrical instrument as defined in claim 8 including a locking flange on said handle for engaging said sheath along said slot in the top of said sheath for locking said blade at said extended osition.

12. An obstetrical instrument as defined in clalm 8 wherein