Description

At time of delivery, the sacrum or lower limbs are the presenting fetal part.

• Frank breech: Fetal hips flexed and knees extended with feet near the face. Sacrum presents first (40–60% of breech presentations at term).
• Footling or incomplete breech: Foot or knee presents first (25–35%).
• Complete breech: Hips and knees flexed. Feet and sacrum present together (5–15%).

Epidemiology

Prevalence
Early gestational age is highly associated with breech presentation, and risk decreases as gestational age advances.

• 22% of fetuses <28 weeks are breech.
• 3–4% of singleton term fetuses
• <10% of breech fetuses at term will spontaneously vert to cephalic.

Genetics
Associated with many fetal anomalies, including anencephaly, head or neck tumors, hydrocephalus, trisomies 21 and 18, Potter syndrome, myotonic dystrophy; associated with maternal müllerian uterine anomalies

Risk Factors

• Early gestational age is number one risk factor.
• History of breech birth
• Low-birth-weight infant
• Female gender
• Fetal anomalies (9% of term breech and 17% of preterm breech)
• Advanced maternal age
• Oligohydramnios, polyhydramnios
• Nulliparity, multiple gestation
• Uterine anomalies, fibroids, or pelvic tumors
• Pelvic contractures or irregularly shaped pelvis, such as android or platypelloid
• Little evidence to support abnormal placentation (placenta previa, cornual-fundal) as a risk factor

General Prevention

• Prenatal folate therapy to decrease risk of neural tube defects
• Tight 1st-trimester glucose control in diabetics decreases anomalies.
• Prenatal screening to diagnose chromosomal or fetal anomalies
• Routine assessment of fetal presentation at 36 weeks to afford time for trial of external cephalic version (ECV)

Commonly Associated Conditions

• Increased risk of cord prolapse (0.4% in cephalic presentation compared with 0.5% in frank breech, 4–6% in complete breech, and 15–18% in footling breech)
• Congenital hip dysplasia has higher incidence in infants with breech presentation at term; more common in female infants than male