Obstetric Forceps. Types of Forceps Operations

It is an instrument designed for extraction of the head of the child. Obstetric forceps are used to apply traction to the head of a viable fetus. The main purpose of this operation is extraction of the fetus by the head.

The Fenomenov modification of the Simpson forceps is now commonly used (Fig. 224). The forceps consist of 2 branches crossing in their middle point. Each branch comprises the following three parts:
- fenestrated blade, or spoon, by which the head is grasped;
- a lock by which the forceps branches are immobilized;
- the handles provided with prominences (the so-called Busch’s hooks) which facilitate the grasp of the surgeon’s hands on the forceps during extraction.

The forceps have two curves, namely the cephalic and the pelvic curve. The cephalic curve is in the apposition to the curvature of the fetal head, while the pelvic curve coincides with the curvature of the pelvic axis.

The length of the forceps is about 35 cm. The handles are a heavier part of the forceps; the length of the handles is about 15 cm. The length of the blades is about 20 cm. The diameter of the cephalic curve between two blades is 11 cm, the distance between the horizontal plane and the apex of the blade of the forceps is 2.5 cm.

Fig. 224. The Fenomenov modification of the Simpson forceps

The forceps may be used for:
- urgent termination of labor for the sake of the maternal and fetal safety;
- substitution of maternal bearing down efforts with extractive efforts of the surgeon.

The operation may be performed according to plan, or it may be urgent.

Indications are as follows:

· Secondary inertia (weak pains) without any effect of medicamental treatment;

· Fetal distress (hypoxia, asphyxia) without any effect of treatment;

· Endometritis of labor.

· Hemorrhages in the 2^nd stage of labor.

· Severe forms of preeclampsia, eclampsia.

· Severe forms of extragenital diseases with decompensation (grave diseases of cardiovascular system and lungs, grave myopia (more than 8 diopters), bronchial asthma, etc.)

Application of forceps should be made under special conditions. Thus, requisite conditions are:

· Full dilation of the cervix.

· Ruptured fetal membrane.

· The fetal head is of normal size (neither small as in a premature fetus, nor large as in a giant fetus or in a hydrocephalus).

· Normal pelvic architecture (normal pelvic sizes).

· The head is in the pelvic cavity or at its outlet.

· Viable fetus.

Types of Forceps Operations. The operations are classified according to the station of the fetal head at which the forceps are applied.

· High forceps delivery. The head lies free above the plane of the inlet and can barely be reached (freely moveable or floating head). The head may be entering the pelvis, but its lowest portion has not descended to the level of the ischial spines. Whatever the case is, the head is unengaged because its biparietal diameter has not passed the plane of the pelvic inlet (Fig 225). If that's the case the operation is named “inlet forceps” operation (or operation with a freely moveable (floating) head above the brim). This type of forceps operation is not useful nowadays.

Fig. 225. Area of inlet forceps (non-useful)

- High midforceps deliveries - the biparietal diameter of the head has passed through the inlet, and lies at the level of 2nd plane of pelvis, but remains above the level of ischial spines. The lowest portion of the head (denominator) lies between the level of the ischial spines and perineal floor. The occiput has begun to rotate toward the anterior quadrant of the pelvis (Fig. 226). This type of forceps delivery is named atypical forceps; it is very difficult to perform. It is practically never performed nowadays.

Fig. 226. Area of high- mid forceps. The head is on the 2 plane of pelvis

- Low midfporceps delivery – biparietal diameter has passed the 2nd plane of the pelvis and lies at a level of ischial spines. The sagittal suture may lie in one of the oblique diameter or in the anteroposterior diameter of this plane of the pelvis (Fig. 227). This type of forceps delivery is named typical forceps; it is mostly an elective operation with the aim of substitution of expulsive pain caused by maternal diseases and complications.

Fig. 227. Area of low-mid forceps. Biparietal diameter lies at the level of ischial spines

- Outlet forceps delivery – it is a variety of low forceps operation when the forceps are applied to the fetal head lying on the pelvic floor and is visible at the introitus in between contractions. The sagittal suture should lie in anteroposterior diameter of the outlet. The best conditions for application of forceps are when the head is descended to the pelvic outlet (Fig. 228).

Fig. 228. Area of outlet forceps. The fetal head lies on the pelvic floor