When the buttocks of the fetus enter the pelvis before the head, the presentation is breech. The term probably derives from the same word as britches, which described a cloth covering the loins and thighs. Breech presentation is more common remote from term because the bulk of each fetal pole is more similar. Most often, however, as term approaches, the fetus turns spontaneously to a cephalic presentation because the increasing bulk of the buttocks seeks the more spacious fundus. But, breech presentation persists in 3 to 4 percent of singleton deliveries at term (Fig. 24-1). For example, the annual rate of breech presentation at delivery in nearly 270,000 singleton newborns at Parkland Hospital has varied from only 3.3 to 3.9 percent during the past 20 years.
Prevalence of breech presentation by gestational age at delivery in 58,842 singleton pregnancies at the University of Alabama at Birmingham Hospitals, 1991 to 2006. (Used with permission from the Center for Women's Reproductive Health, University of Alabama at Birmingham.)
As term approaches, the uterine cavity usually accommodates the fetus in a longitudinal lie with the vertex presenting. Factors other than gestational age that predispose to breech presentation include hydramnios, high parity with uterine relaxation, multiple fetuses, oligohydramnios, hydrocephaly, anencephaly, previous breech delivery, uterine anomalies, placenta previa, fundal placental implantation, and pelvic tumors. Vendittelli and colleagues (2008) recently described a twofold incidence of breech presentation and prior cesarean delivery.
The varying relations between the lower extremities and buttocks of breech presentations form the categories of frank, complete, and incomplete breech presentations. With a frank breech presentation, the lower extremities are flexed at the hips and extended at the knees, and thus the feet lie in close proximity to the head (Fig. 24-2). A complete breech presentation differs in that one or both knees are flexed (Fig. 24-3). With incomplete breech presentation, one or both hips are not flexed, and one or both feet or knees lie below the breech, such that a foot or knee is lowermost in the birth canal (Fig. 24-4). Footling breech is an incomplete breech with one or both feet below the breech.
Frank breech presentation.
Complete breech presentation.
Incomplete breech presentation.
In perhaps 5 percent of term breech presentations, the fetal head may be in extreme hyperextension. These presentations have been referred to as the stargazer fetus, and in Britain as the flying foetus. With such hyperextension, vaginal delivery may result in injury ...