FIGURE 29-7 A. The forceps are symmetrically placed and articulated. B.The vertex is OA. (Reproduced with permission from Yeomans ER: Operative vaginal delivery. In Yeomans ER, Hoffman BL, Gilstrap LC III, et al (eds): Cunningham and Gilstrap's Operative Obstetrics, 3rd ed. New York, McGraw-Hili Education, 201•7.)
FIGURE 29-8 Incorrect application of forceps. A. One blade over the occiput and the other over the brow. Forceps cannot be locked.
B.With incorrect placement, blades tend to slip of with traction.
begins to bulge. When the head is at 0 to + 2 of + 5 sta tion, the initial direction of traction is quite posterior, almost toward the Roor. With head descent, the vector of forces changes continuously (Fig. 29-10). As a teaching tool for this, a Bill axis traction device can be attached over the finger guards of most forceps. he instrument has an arrow and indicator line. When the arrow points directly to the line, traction is
FIGURE 29-9 A. If LOA, the vertex is rotated (arrow) from this position to OA (B). (Reproduced with permission from Yeomans ER: Operative vaginal delivery. In Yeomans ER, Hoffman BL, Gilstrap LC III, et al (eds): Cunningham and Gilstrap's Operative Obstetrics, 3rd ed. New York, McGraw-Hili Education, 201o7.)
FIGURE 29-10 With low forceps, the direction of gentle traction for delivery of the head is indicated (arrow). The vector changes with fetal descent.
along the path of least resistance. With traction, as the vulva is distended by the occiput, an episiotomy may be performed if indicated. Additional horizontal traction is applied, and the handles are then gradually elevated. As the handles are raised, the head is extended. During the birth of the head, mechanisms of spontaneous delivery should be simulated as closely as possible.
The force produced by the forceps on the fetal skull is a function of both traction and compression by the forceps, as well as friction produced by maternal tissues. It is impossible to ascertain the amount of force exerted by forceps for an individual patient. Traction should therefore be intermittent, and the head should be allowed to recede between contractions, as in spontaneous labor. Except when urgently indicated, as in severe fetal bradycardia, delivery should be suiciently slow, deliberate, and gentle to prevent undue head compression. It is preferable to apply traction only with each uterine contraction. Maternal pushing will augment these eforts.
After the vulva has been well distended by the head, the delivery may be completed in several ways. Some clinicians keep the forceps in place to control the head. If this is done, however, the blade volume adds to vulvar distention, thus from that in which they were originally placed. The fingers of the right hand, covered by a sterile towel, bolster the perineum. The thumb is placed directly on the head to prevent sudden egress. (Reproduced with permission from Yeomans ER: Operative vaginal delivery. In Yeomans ER, Hoffman BL, Gilstrap LC III, et al (eds): Cunningham and Gilstrap's Operative Obstetrics, 3rd ed. New York, McGraw-Hili Education, 201o7.) increasing the likelihood of laceration or necessitating a large episiotomy. To prevent this, the forceps may be removed, and delivery is then completed by maternal pushing (Fig. 29-11). Importantly, if blades are disarticulated and removed too early, the head may recede and lead to a prolonged delivery. Delivery in some cases may be aided by addition of the modiied Ritgen maneuver.