Near the end of pregnancy, the baby normally assumes a cephalic presentation (95% of the time), meaning the baby is head-down; 4% of the time, the baby is in a breech presentation, with the buttocks closest to the cervix and the head up.

Obstetricians identify three types of breech presentations according to the relationship of the baby's hips and legs to its body:

 

  • Complete Breech Presentation. The legs are flexed at the knees so that the fetus appears to be sitting cross-legged, and the buttocks themselves are down against the bottom of the uterus and cervix.
  • Incomplete Breech Presentation. One of the legs is extended more or less at the knee so that one of the feet is further down in the uterus or against the cervix. This is also called a footling breech, since one or both of the feet may be the presenting part.
  • Frank Breech Presentation. The hips of the fetus are flexed and the legs extended at the knees so that the feet of the fetus are up around the face and the buttocks are down against the lower-most portion of the uterus.

 

Although most breech babies are normal, some are in a breech presentation because of an accompanying defect, which is about three times more common than in a cephalic presentation. There is some evidence that all breech babies, whether delivered by cesarean or vaginal delivery, have an increased risk of delayed motor development. External cephalic version (ECV) is the first step attempted when breech presentation is encountered before labor, yet close to term, since ECV is more difficult after labor has begun. This is a procedure where the obstetrician pushes on the mother's abdomen in a certain manner to facilitate rotation of the baby's head from up to down. Usually an injection is given prior to this procedure to relax the uterus and help the baby rotate. Sometimes this can induce labor or lower the baby's heart rate, which is why it is only performed close to term. If ECV is unsuccessful, options include cesarean section or attempted vaginal breech delivery.

Based on results of an international trial that randomized women at term with a breech fetus to anticipated vaginal delivery or cesarean section, in 2001 the of Obstetricians and Gynecologists released a statement essentially mandating that all women with a breech fetus who are not close to delivery should undergo a cesarean delivery. The study found that the risk of neonatal death and disability was dramatically lower in the group that underwent a cesarean section. Some well-respected obstetricians have taken issue with this statement due to the fact that it is based only a single, well-designed trial and the findings have not been reproduced.

Breech presentation is more common earlier in pregnancy and is found in about 10 to 15% of women with premature labor symptoms or preterm premature rupture of the membranes. Breech presentation is also more common in women with abnormalities of the uterus such as fibroids, a bicornuate uterus, or a uterine septum. Overall, the fetal and neonatal death rate is 5 to 10% for breech presentations, compared to less than 3% for cephalic presentations, mainly due to other complications, such as prematurity or birth defects, rather than from the breech presentation itself. In other words, adverse conditions in pregnancy lead to a breech presentation, not vice-versa.