Breech birth

Lore & Background

The cause of breech presentation involves three gestational periods. Until the 24th week, presentations change frequently, with equal probability of breech or cephalic at delivery. From the 25th to 35th week, cephalic presentation increases, and the probability that the presentation will persist at delivery rises gradually. After the 36th week, incidence stabilizes at 3–4% breech. Failure to turn can result from endogenous factors (fetal inability to move) or exogenous factors (insufficient intrauterine space).

Reader's Guide

Breech birth remains a significant obstetric challenge, particularly in developing countries where resources for safe vaginal breech delivery or caesarean section may be lacking. The condition is associated with numerous fetal, placental, and maternal medical conditions, with incidence ranging from 4% to 50% depending on the entity. Complications such as umbilical cord prolapse and head entrapment can lead to oxygen deprivation and permanent neurological damage. While caesarean section is generally considered safer, the article notes that a fast vaginal delivery might reduce oxygen supply risk, but there is insufficient research to confirm this, and a quick delivery might cause more harm. The Løvset manoeuvre is one technique used to manage arm extension during delivery.

Did You Know?

• Among full-term head-down babies, cord prolapse occurs in 0.4 percent, but in footling breech it occurs in 15 percent.
• The highest probability of breech presentation (50%) is seen in conditions such as Prader–Willi syndrome, amelia, and multiple pituitary hormone deficiency.
• Women with previous caesarean deliveries have twice the risk of breech presentation at term compared to women with previous vaginal deliveries.
• The fetal bitrochanteric diameter at full term is about the same as the biparietal diameter, meaning the hips and head are similarly sized.

Prevalence and the Risk Landscape

Breech birth occurs when a baby is delivered buttocks-first or feet-first rather than in the standard head-down orientation. At full term—between 37 and 40 weeks of pregnancy—roughly 3 to 4 percent of expectant mothers carry a baby in this position. Because the non-standard orientation carries a higher-than-average risk of complications for the infant, breech deliveries are broadly classified as higher-risk events. The phenomenon is not unique to humans; dogs, horses, and numerous other mammals also experience breech presentations, a topic that falls under veterinary obstetrics. A significant practical challenge arises in lower-resource settings, where clinicians and midwives frequently lack the specialized equipment or disposable hospital supplies needed to safely manage a vaginal breech delivery. At the same time, routing every breech case through caesarean section is itself difficult to implement where surgical infrastructure is scarce, creating a genuine dilemma in global maternal care.

The Three-Phase Timeline of Fetal Position

The trajectory of how a baby settles into its final presentation unfolds across three distinct gestational phases. In the first phase, extending to the 24th week, the fetus shifts toward a longitudinal lie, and breech and head-down positions occur in roughly equal measure. Presentations change frequently during this window, meaning a breech baby at 20 weeks has the same odds of arriving head-first at delivery as one in cephalic position. The second phase, spanning weeks 25 through 35, sees cephalic presentations gradually become more common while breech incidence declines. Importantly, whatever position the baby occupies during this stretch carries a growing—though still moderate—probability of persisting through to birth, and this probability rises identically for both orientations. By the third phase, from week 36 onward, the proportions lock in: breech stabilizes near 3 to 4 percent and cephalic near 95 percent. A breech outcome at delivery ultimately reflects the fetus's failure to rotate, driven by either its own limited mobility or insufficient room within the uterus.

Classification by Leg Position and Sacral Orientation

Breech presentations are further subdivided based on how the baby's lower limbs are arranged. In a frank breech—sometimes called an extended breech—the legs stretch upward alongside the abdomen with knees straight and feet resting near the ears; this is the most frequently encountered variant. A complete breech, or flexed breech, presents as though the infant is sitting cross-legged, with hips and knees both bent. The footling breech is distinct in that one or both feet lead the delivery rather than the pelvis, a pattern seen more often in premature or preterm infants. A rarer kneeling breech involves the baby arriving knees-first. Beyond leg configuration, clinicians also classify breech by the position of the sacrum relative to the mother's pelvis. Sacro-anterior, sacro-transverse, and sacro-posterior orientations all exist, with left sacro-anterior being the most common. The sacro-anterior alignment is generally regarded as the most favorable for delivery compared to the other sacral positions.

Umbilical Cord Prolapse and Delivery Decisions

One of the most serious complications associated with breech delivery is umbilical cord prolapse, a risk that is particularly elevated in complete, footling, and kneeling breech presentations. The mechanism is anatomical: because the baby's lowest parts do not fully seal the dilated cervix, the umbilical cord can slip ahead of the fetus once the amniotic membranes rupture. Once the cord descends and becomes compressed, oxygen supply to the baby drops sharply, creating an emergency that demands immediate delivery. In such scenarios, caesarean section is the likely recommended intervention, and any delay in getting the baby out risks brain damage. For comparison, among full-term head-down babies, cord prolapse is quite rare, affecting only about 0.4 percent of deliveries. The overall clinical picture—higher complication risk, the need for rapid decision-making, and the resource demands of safe management—explains why the majority of breech babies are now delivered surgically rather than vaginally, even though this approach presents its own logistical challenges in under-resourced healthcare systems.