Obstetrics and Gynecology - A.M. Hromova 2000

Operative Obstetrics
Delivery Operations
Obstetric Forceps

In cases where maternal pushing efforts are insufficient for childbirth, or There is a threat to the mother and fetus requiring a rapid delivery, instruments known as obstetrical forceps must be used. The purpose of applying obstetrical forceps is to extract the fetus by the HEAD in accordance with the natural mechanism of labor.

Obstetrical forceps were invented as early as the 17th century by Chamberlen, but he did not publish his invention, and therefore the priority of discovering obstetrical forceps is credited to the Geneva surgeon and anatomist Palfyn. In Russia, forceps were first applied by Moscow University Professor Erasmus in 1765. The Introduction of this Procedure into obstetrical practice was promoted by the pioneering native obstetrician N.M. Maxinovich-Ambodik. The most widespread model is the English Simpson-Phenomenov forceps. These are short forceps with a pelvic curve corresponding to the curvature of the leading birth canal and a head curve designed to grasp the fetal head.

Each blade (more commonly called a spoon) of the forceps consists of three parts: the upper part, or the spoon proper; the middle part, or the lock; and the lower part, or the shank. The spoon features an oval opening, 11 cm long and 5 cm wide. The fenestration is framed by Ribs (upper and lower) that round off at the top. When the locks are closed, the tips of the forceps are located at a distance of 2.5 cm from each other, while the distance between the most remote points of the head curve is 8 cm, which corresponds to the large transverse diameter of the head, taking into account its configuration. At the other end of the spoon is the shank, one edge of which (the inner) is flat, and the second (outer) is ribbed. On the outer surface of the shanks near the lock are the so-called Busch hooks. The inner edge of the shank presses against the other when the spoons are closed, while the protrusions on the outer edges serve as finger Supports for the obstetrician's hands. Both spoons feature a lock in the middle, by means of which they are locked together. The forceps weigh 500 g and have a length of 35 cm.

The forceps blades are differentiated by the following features:

- on the left blade, the lock and lock plate are located on top, while on the right they are on the bottom;

- if the forceps are placed on a table (with the tips pointing upward), the Busch hooks and ribbed protrusions on the shank of the left blade will be on the left, and on the right blade, on the right.

Forceps must serve exclusively as a grasping and traction instrument that reinforces or replaces insufficient or absent vis a tergo (propulsive force from behind).

The application of obstetrical forceps can be of two types: outlet and cavity.

Outlet forceps are applied to the head when it is stationed in the plane of the pelvic outlet. Upon external obstetrical examination, the head is not palpable above the pelvic inlet. The cervical furrow is not defined. The head has completed internal rotation (rotatio), reached the pelvic floor, and the diameter bitemporalis is below the plane of the narrow cavity of the pelvis. The head fills the entire pelvic cavity. The sagittal suture lies in the direct diameter of the pelvic outlet.

Cavity forceps are used if the head is stationed in the narrow part of the pelvic cavity. Upon external obstetrical examination, the head is not identified above the pelvic inlet. The cervical furrow is at the level of the symphysis (flush). Upon vaginal examination, the ischial spines (spinae ossis ischii) are not reached. The upper two-thirds of the sacral surface and the entire surface of the symphysis are filled by the head. The biparietal diameter occupies the plane of the narrow part of the lesser pelvis cavity. The head has not completed internal rotation. The sagittal suture lies in one of the oblique diameters of the pelvis, close to the direct diameter.

Indications for the application of obstetrical forceps are associated with conditions and complications that require rapid termination of labor in the best interests of the mother and fetus.

Indications for the application of forceps on the part of the mother:

— uterine inertia during prolonged stasis of the head in a single pelvic plane and lack of response to medical stimulation;

— endometritis during labor;

— severe disorders of The Cardiovascular system, Lungs, Liver, Kidneys, or visual Organs that necessitate avoiding physical exertion by the woman during labor;

— severe forms of gestosis;

— premature Separation of a normally implanted Placenta;

— other maternal conditions requiring urgent delivery.

Indications for the application of forceps on the part of the fetus:

— stage II-III Hypoxia, which may arise during labor due to prolapse and compression of the umbilical cord loop, velamentous insertion of the cord, nuchal cord entanglement with tension, bleeding associated with premature detachment or partial Placenta Previa, or As a result of other causes.

Conditions for the application of forceps:

— living, term fetus;

— the fetal head must correspond to average dimensions;

— the amniotic sac must be ruptured, and the membranes pushed back above the fetal head;

— full dilation of the uterine cervix;

— correspondence between the dimensions of the pelvis and the fetal head;

— emptied Urinary Bladder;

— the fetal head must be positioned at the pelvic outlet or in the plane of the narrow pelvic cavity;

— adequate anesthesia;

— the obstetrician must be competent in forceps delivery.

Anesthesia may be general or local (pudendal block with 60 ml of 0.5% novocaine solution on each side). The choice of anesthesia depends on the capabilities of the obstetric department, as well as the indications for the application of obstetrical forceps.

General Principles of applying obstetrical forceps

The rules governing the application of obstetrical forceps are known as the triple rules.

First rule: the forceps are applied such that the left blade is introduced into the birth canal first with the left hand into the left side of the pelvis (the "three lefts" rule), followed by the right blade with the right hand into the right side of the pelvis ("three rights").

Second rule: the forceps should be applied so that:

— the tips of the blades are directed toward the leading point;

— the forceps blades grasp the head along the large oblique diameter and lie biparietally;

— the leading axis of the fetal head lay in the plane of the forceps.

The technique of applying outlet obstetric forceps consists of the following stages:

Insertion of the blades.

Locking the forceps.

Test traction.

Delivery of the head.

Removal of the forceps.

The forceps are designed so that their major curve adapts to the sides of the fetal head. The biparietal diameter of the fetal head corresponds to the greatest distance between the forceps blades. The blades should be applied biparietally, parallel to the long axis of the head, i.e., its mento-occipital diameter (diameter mentoaccipitalis).

1. Insertion of the blades

Before the procedure, the correspondence of the forceps blades is checked. They are assembled together. Afterwards, the labia pudendi are parted with the left hand, and four fingers of the right hand are inserted along the left vaginal wall so that the tip of the blade lies in the groove between the fingers of the hand introduced into the Vagina, while the handle is directed toward the opposite inguinal fold.

With the left hand, the handle of the left forceps blade is grasped like a writing pen, supporting the lower edge from below with the thumb of the right hand. When inserting the forceps blade into the vaginal introitus, the thumb of the right hand pushes the lower edge of the blade. The blade should glide between the index and middle fingers of the right hand. The major curve of the forceps blade should be snugly apposed to the fetal head without injuring the margin of the uterine cervix. The right blade is inserted into the right side of the pelvis with the right hand. When properly applied, the forceps blades should be positioned at two diametrically opposite points, the handles converge toward the midline and rest against the Perineum. The fenestrae of the blades correspond to the ear regions, and the hooks are located in the transverse diameter.

2. Locking the forceps

Each handle of the forceps is grasped with the corresponding hand. Having grasped the handles, the obstetrician places the thumb along the entire anterior surface of the handle so that its tip falls on the lateral hook, while the thenar eminence rests on the anterior end of the handle. Bringing the handles together, the forceps are locked. A prerequisite for locking the forceps is the symmetrical positioning of both handles. Such positioning can only be achieved when the inner smooth surfaces of the handles are parallel to each other and the lateral hooks lie on a single straight line. If these conditions are not met, locking the forceps will be impossible.

3. Trial Traction

Once the forceps are locked, the operator proceeds to trial traction. The obstetrician places the right hand on top of the handles and over the side hooks. The left hand should rest on top of the right hand, with the index finger pressed against the fetal head near the leading point. The right hand then carefully performs the first traction. The traction should pull the forceps, the left hand, and the fetal head synchronously. If the distance between the index finger of the left hand and the leading point begins to increase during traction, it indicates that the lock is unstable and the forceps will eventually slip off.

4. Extraction of the Head with Forceps

Actual traction is the penultimate step of the procedure. Traction must guide the head along the exact anatomical axes corresponding to the normal mechanisms of labor. It should be applied smoothly, without jerking, with a gradual increase in pulling force.

It is crucial to maintain the periodicity of tractions: they should be performed exclusively during uterine contractions. In the intervals between contractions, the obstetrician should merely support the forceps blades by hand, lightly holding them at the lock.

Three positions are distinguished during the execution of tractions:

Position I is performed while the obstetrician is seated. The hands hold the forceps as follows: the left hand grasps the handles from below, while the right hand rests on top of them, with the middle finger placed in the space between the blades, and the flexed 2nd and 3rd fingers resting on the Busch hooks. Tractions are directed horizontally and downwards until the fetal head approaches the perineum and begins to bulge it.

Position II is applied during the crowning of the head. Tractions are directed towards the operator, bringing the occiput under the Pubic Symphysis. This maneuver is also performed while seated, with the same hand placement, except that the left hand now rests on top of the forceps while the right hand grasps them from below. An Episiotomy may be performed during this stage.

Position III: The physician stands up and changes the hand position (holding the forceps with the full grip of one hand, or according to Tsovyanov, so that the flexed 2nd and 3rd fingers of both hands clasp the handles in an alternating staggered pattern at the level of the Busch hooks, the 4th and 5th fingers are positioned above them, and the thumbs press against the anterior part of the handles from below). Tractions are performed in a steep, upward-arcing motion.

5. Removal of the Forceps

Once the parietal eminences are delivered, the forceps can be removed and the head extracted manually. The forceps are removed in the reverse order of their application—first the right blade, then the left blade, using hand movements parallel to the opposite groin. Next, the head is delivered manually, just as in spontaneous vertex delivery.

If an episiotomy was performed during the application of the forceps, the blades are removed before the head crowns. Following the procedure, Manual Exploration of the uterine cavity is mandatory due to the high risk of ruptures.

The technique of applying cavity forceps is similar, though it has several specific features. Cavity forceps are applied to the fetal head when it is positioned in the narrow plane of the pelvic cavity. The sagittal suture of the fetal head lies in either the right or left oblique diameter of the pelvic cavity. The forceps are applied in the oblique diameter of the pelvis that is opposite to the one occupied by the fetal head. In the first position, when the sagittal suture corresponds to the right oblique diameter, the forceps are placed in the left one. In this case, the left blade remains posterior, while the right blade is guided forward (the 'wandering' blade). In the second position, the opposite is true: the forceps are applied in the right oblique diameter, and the 'wandering' blade is the left one.

Traction completes the internal Rotation of the head by 45°. The direction of traction is initially downward, and then, as the head crowns, toward the operator and upward. This procedure must be performed by a highly qualified specialist.

Complications during the application of obstetric forceps

1. The introitus vaginae may occasionally be too narrow to allow the insertion of the examining fingers. In such cases, the vaginal entrance must be enlarged via a vaginoperineal incision before the operation begins.

2. Difficulties in inserting the blades can sometimes be caused by significant molding of the fetal head and a mismatch between the head curve of the blades and the spherical contour of the head.

3. In some cases, difficulties may arise when locking the forceps. This occurs when the blades do not lie in the same plane. If this happens, their position should be adjusted by manipulating the lower blade so that the forceps are not applied too low.

4. The forceps may slip either directly forward (vertical slip) or downward (horizontal slip). It is necessary to remove the forceps immediately and reapply them.

5. Difficulties sometimes arise during the extraction of the fetal head due to vaginal rigidity.

Complications associated with the application of obstetric forceps

1. Trauma to the maternal birth canal:

- rupture of the perineum, vaginal walls, and cervix;

- separation of the pubic symphysis;

- formation of vesicovaginal and rectovaginal fistulae;

- injury to peripheral nerves.

2. Fetal injuries:

- trauma to fetal soft Tissues;

- scalp lacerations and avulsions in the fetus;

- Facial Nerve palsy;

- bone injuries: ranging from compression to fractures inclusive;

- Brain compression;

- intracranial Hemorrhage.

Review Questions

1. Who invented obstetric forceps?

2. Who was the first to use obstetric forceps in Russia?

3. Design of obstetric forceps.

4. Indications for the application of obstetric forceps.

5. Conditions required for the application of obstetric forceps.

6. Anesthesia for the application of obstetric forceps.

7. Which hand is used to insert the right blade of the obstetric forceps?

8. Which hand is used to insert the left blade of the obstetric forceps?

9. Along which diameter of the fetal head should obstetric forceps be applied?

10. In which case are the forceps referred to as "cavity forceps"?

11. In which case are the forceps referred to as "outlet forceps"?

12. Name the procedural steps for applying obstetric forceps.

13. In which pelvic plane/diameter are outlet obstetric forceps applied?

14. In which pelvic plane/diameter are cavity obstetric forceps applied?

15. State the first triple rule.

16. State the second triple rule.

17. What complications may arise during the application of obstetric forceps?