Near term, the typical fetus spontaneously assumes a cephalic presentation. However, if the fetal buttocks or legs enter the pelvis before the head, the presentation is breech. At term, breech presentation persists in 2 to 5 percent of singleton deliveries (Bin, 2016; Cammu, 2014; Toijonen, 2019). Breech delivery of a second twin is discussed in Chapter 48 (p. 856).
The categories of frank, complete, and incomplete breech presentations differ in their varying relations between the lower extremities and buttocks. With a frank breech, lower extremities are flexed at the hips and extended at the knees, and thus the feet lie close to the head (Fig. 28-1). With a complete breech, both hips are flexed, and one or both knees are also flexed (Fig. 28-2). With an incomplete breech, one or both hips are extended. As a result, one or both feet or knees lie below the breech, and thus a foot or knee is lowermost in the birth canal. A footling breech is an incomplete breech with one or both feet below the breech.
Frank breech presentation.
Complete breech presentation.
Of singleton term breech fetuses, the neck may be extremely hyperextended in perhaps 5 percent, and the term stargazing fetus is used (Cimmino, 1975). With transverse lie and similar hyperextension of the fetal neck, the term flying fetus is applied. With these, fetal or uterine anomalies may be more prevalent and are sought if not previously identified (Phelan, 1983; Shipp, 2000). With hyperextension, vaginal delivery can injure the cervical spinal cord. Thus, if identified at term, cesarean delivery is indicated (Westgren, 1981). However, cases of spinal cord injury have been reported following uneventful cesarean delivery of breech fetuses. Here, the flexion itself may be implicated (Hernandez-Marti, 1984; Weinstein, 1983).
Understanding the clinical settings that predispose to breech presentation can aid early recognition. This fetal lie is more common remote from term, as earlier in pregnancy each fetal pole has similar bulk (Toijonen, 2019). Multifetal gestation is another (Chap. 48, p. 856). With singletons, other factors include extremes of amnionic fluid volume, fetal anomalies, structural uterine abnormalities, placenta previa, nulliparity, increased maternal age, female fetal gender, prior breech delivery, and size that is small for gestational age (Bin, 2016; Cammu, 2014; Noli, 2019; Roberts, 1999). One study found that following one breech delivery, the recurrence rate for a second breech presentation was 10 percent, and for a subsequent third breech it was 28 percent (Ford, 2010).