With this, an extremity prolapses alongside the presenting part, and both present simultaneously in the pelvis (Fig. 23-11). Goplerud and Eastman (1953) identiied a hand or arm prolapsed alongside the head once in every 700 deliveries. Much less common was prolapse of one or both lower extremities alongside a cephalic presentation or a hand alongside a breech. At Parkland Hospital, compound presentations were identiied in only 68 of more than 70,000 singleton fetuses-an incidence of approximately 1 in 1000. Causes of compound presentations are conditions that prevent complete occlusion of the pelvic inlet by the fetal head, including preterm labor.
In most cases, the prolapsed part should be left alone, because most often it will not interfere with labor. If the arm is prolapsed alongside the head, the condition should be observed closely to ascertain whether the arm retracts out of the way with descent of the presenting part. If it fails to retract and if it appears to prevent descent of the head, the prolapsed arm should be pushed gently upward and the head simultaneously downward by fundal pressure.
In general, rates of perinatal mortality and morbidity are increased as a result of concomitant preterm delivery, prolapsed cord, and traumatic obstetrical procedures. Serious injury to the forearm is rare (Kwok, 2015; Tebes, 1999).
Dystocia, especially if labor is prolonged, is associated with a higher incidence of several common obstetrical and neonatal complications. Inection, either intrapartum chorioamnionitis or postpartum pelvic infection, is more common with desultory
FIGURE 23-11 Compound presentation. A. The left hand is lying in front of the vertex. With further labor, the hand and arm may retract from the birth canal, and the head may then descend normally. B. Photograph of a small 34-week fetus with a compound presentation that delivered uneventfully with the hand presenting first. (Used with permission from Dr. Elizabeth Mosier.) and prolonged labors. Pospartum hemorrhage rates from atony are increased with prolonged and augmented labors. Uterine tears with hysterotomy also occur at greater incidence if the fetal head is impacted in the pelvis.
Uterine rupture is another risk. Abnormal thinning of the lower uterine segment creates a serious danger during prolonged labor, particularly in women of high parity and in those with a prior cesarean delivery. When disproportion is so pronounced that there is no engagement or descent, the lower uterine segment becomes increasingly stretched, and rupture may follow. In such cases, the normal contraction ring is usually exaggerated, like that shown in Figure 23-10.
Such pathological retraction rings are localized constrictions of the uterus that develop in association with prolonged obstructed labors. Seldom encountered today, the pathological retraction ring o/Bandl is associated with marked stretching and thinning of the lower uterine segment. In contemporary practice, after birth of a irst twin, a pathological ring may still develop occasionally as an hourglass constriction of the uterus. he band may be seen clearly as a uterine indentation and signifies impending rupture of the lower uterine segment. he ring can sometimes be relaxed and delivery efected with appropriate general anesthesia, but for the second twin (Chap. 45, p. 890).
Fistula ormation may result from dystocia, as the presenting part is irmly wedged into the pelvic inlet. Tissues of the birth canal lying between the leading part and the pelvic wall may be subjected to excessive pressure. Because of impaired circula tion, necrosis can result and become evident several days after delivery as vesicovaginal, vesicocervical, or rectovaginal istulas.
Most often, pressure necrosis follows a very prolonged second stage. Such fistulas are rarely seen today except in undeveloped countries.