With full cervical dilation, which signiies the onset of the second stage, a woman typically begins to bear down. With descent of the presenting part, she develops the urge to defecate. Uterine contractions and the accompanying expulsive forces may now last 1 minute and recur at an interval no longer than 90 seconds. As discussed earlier, the median duration of the second stage is 50 minutes in nulliparas and 20 minutes in multiparas, although the interval can vary. Monitoring intervals of the fetal heart rate were discussed on page 436, and interpretation of second-stage electronic fetal heart rate patterns is discussed in Chapter 24 (p. 469).
In most cases, bearing down is reflexive and spontaneous during second-stage labor. Occasionally, a woman may not employ her expulsive forces to good advantage and coaching is desirable. Her legs should be half-flexed so that she can push with them against the mattress. When the next uterine contraction begins, she is instructed to exert downward pressure as though she were straining at stool. A woman is not encouraged to push beyond the completion of each contraction. Instead, she and her fetus are allowed to rest and recover. During this period of actively bearing down, the fetal heart rate auscultated during the contraction is likely to be slow but should recover to normal range before the next expulsive efort. Fetal and obstetrical outcomes appear to be unafected whether pushing is coached or uncoached during second-stage labor (Bloom, 2006; Tuuli, 2012). Bloom and colleagues (2006) studied efects of actively coaching expulsive eforts in women without epidural analgesia. hey reported that although the second stage was slightly shorter in coached women, no other maternal advantages were gained.
Several positions during the second stage have been recommended to augment pushing eforts. Eason and colleagues (2000) reviewed various posltlons and their efect on the incidence of perineal trauma. They found that the supported upright position had no advantages over the recumbent one. Upright positions include sitting, kneeling, squatting, or resting with the back at a 30-degree elevation. In women with regional analgesia, one recent randomized trial found higher vaginal delivery rates in those in a recumbent position compared with an upright one-41 versus 35 percent (The Epidural and Position Trial Collaborative Group, 2017). In women without epidural analgesia, Gupta (2017) in their review compared upright positions with supine or lithotom) positions and their efect on labor. Upright positions ofered a slightly shorter interval to delivery as well as fewer episiotomies and operative vaginal deliveries. However, rates of blood loss > 500 mL and perhaps of second-degree lacerations were increased. Berghella and coworkers (2008) hypothesized that parity, less intense aortocaval compression, improved fetal alignment, and larger pelvic outlet diameters might explain these indings. In an earlier study, a 20-to 30-percent increase in the area of the pelvic outlet was noted with squatting compared with the supine position (Russell, 1969). Finally, Babayer and associates (1998) cautioned that prolonged sitting or squatting during the second stage may cause neuropathy of the common fibular (formerly common peroneal) nerve.
As the head descends through the pelvis, the perineum begins to bulge and the overlying skin becomes stretched. Now the scalp of the fetus may be visible through the vulvar opening. At this time, the woman and her fetus are prepared for delivery, which is described in Chapter 27 (p. 516).
An orderly and systematic approach to labor management results in reproducible beneficial maternal and perinatal outcomes (lthabe, 2008). Several labor management protocols are subsequently presented. These include those from the National Maternity Hospital in Dublin, from the World Health Organization, and from Parkland Hospital.