The natural culmination of second-stage labor is controlled vaginal delivery of a healthy neonate with minimal trauma to the mother. Vaginal delivery is the preferred route of delivery for most fetuses, although certain clinical settings may favor cesarean delivery. Spontaneous vaginal delivery is typical, however, maternal or fetal complications may warrant operative vaginal delivery as described in Chapter 29. Last, a malpresenting fetus or multifetal gestation in many cases may be delivered vaginally but requires special techniques. These are described in Chapters 28—Breech Delivery and 45—Multifetal Pregnancy.
In general, spontaneous vaginal vertex delivery poses the lowest risk of most maternal and fetal comorbidity. Compared with cesarean delivery, spontaneous vaginal delivery has lower associated rates of maternal infection, hemorrhage, anesthesia complications, and peripartum hysterectomy, among others. In contrast, for women undergoing spontaneous vaginal delivery compared with cesarean delivery, pelvic floor disorders may be increased (Handa, 2011; Rortveit, 2003). Longitudinal studies, however, suggest that initial pelvic floor protection advantages gained from cesarean delivery are lost as women age (Dolan, 2010; Glazener, 2013; Rortveit, 2001). During their State-of-the-Science Conference, the National Institutes of Health panel (2006) summarized that stress urinary incontinence rates after elective cesarean delivery are lower than those following vaginal delivery. However, the duration of this protection is unclear, particularly in older and multiparous populations. This same conference considered the evidence implicating vaginal delivery in other pelvic floor disorders to be weak and not favoring either delivery route.
The end of second-stage labor is heralded as the perineum begins to distend, the overlying skin becomes stretched, and the fetal scalp is seen through the separating labia. Increased perineal pressure from the fetal head creates reflexive bearing-down efforts, which are encouraged when appropriate. At this time, preparations are made for delivery. Some considerations that arise during labor and which are also discussed in Chapter 22 (Management of the Second Stage of Labor) are reiterated. For example, the bladder is palpated, and if it is distended, catheterization may be necessary. Continued attention is also given to fetal heart rate monitoring. As one example, a nuchal cord often tightens with descent and may lead to deepening variable decelerations. Antibiotic prophylaxis against infective endocarditis is not recommended for vaginal delivery in most women with cardiac conditions. Exceptions are in women with cyanotic heart disease or prosthetic valves or both. For these women, prophylaxis as outlined in Table 49-10 (Arrhythmias) is indicated 30 to 60 minutes before the anticipated procedure (American College of Obstetricians and Gynecologists, 2011).
During second-stage labor, pushing positions may vary. But for delivery, dorsal lithotomy position is the most widely used and often the most satisfactory. For better exposure, leg holders or stirrups are used. Corton and associates (2012) found no increased rates of perineal lacerations ...