While most babies settle into a vertex, or head down, position in the last weeks of pregnancy, 3 to 4 percent are oriented in a breech position. This means the baby's buttocks and/or feet are positioned to deliver first.

Breech presentations are more common with multiple pregnancies, in pregnancies where the uterus is abnormally shaped, in pregnancies with too much or too little amniotic fluid and in premature pregnancies. Although most breech babies are perfectly normal, sometimes a baby may maintain a breech position due to a birth defect.

When the breech baby is suspected in the last weeks of pregnancy, an ultrasound may be used to confirm the position. If a breech presentation is verified, an external version may be offered.

An external version is a procedure in which a breech baby is manually rotated to the head-down position. This is usually done by a physician in a hospital and may require premedication to relax the uterine muscle. After assessing the baby's heart rate and checking the baby's position with an ultrasound, the physician attempts to physically guide the baby into the appropriate position.

External version is successful about 65 percent of the time and increases the chances for a vaginal delivery. However, this procedure has some risks. These include fetal heart rate disturbances, rupture of membranes, initiation of labor and placental abruption. Also, some babies will shift back to the breech position in the days or weeks following an external version.

A vaginal breech delivery is more risky than a vertex delivery. Why? The largest and firmest part of a baby is his head. In a vertex delivery, the baby's head slowly accommodates to the shape of the mother's birth canal during birthing. If the head won't fit, a Caesarean section can be safely performed. In a breech delivery, the baby's head has no time to adapt to the shape of the birth canal and can be hard to deliver. There's a small chance of head entrapment, which can be fatal in rare cases.

It's also possible for the baby's shoulders or arms to be overstretched, which can result in temporary or long-term arm movement difficulties. Finally, the umbilical cord, carrying oxygen-rich blood, emerges before the head is delivered in a breech delivery. Once the umbilical cord delivers, blood flow is impaired until the delivery is completed. Subsequently, breech babies typically have lower Apgar scores than babies born vertex.

Although some breech deliveries occur easily, it often requires skill to deliver breech babies safely. Years ago, most obstetricians were well trained in vaginal breech deliveries. As operative deliveries became more common, many doctors opted to deliver breech babies by Caesarean section, preferring to avoid some of the risks associated with vaginal breech deliveries. Recommendations for vaginal or C-section deliveries were often based on the physician's own skill level.

In 2000, there was a study of more than 2,000 term breech babies assigned to either planned vaginal or planned Caesarean deliveries. Researchers found significantly lower rates of neonatal morbidity and mortality in the Caesarean group. They also reported that more than 40 percent of the mothers assigned to a planned vaginal delivery required a Caesarean section due to inadequate progress during labor, a non-reassuring fetal heart rate pattern, umbilical cord prolapse or other problems.

Because of the higher rates of complications in the vaginal birth group, the American College of Obstetricians and Gynecologists now suggests that planned vaginal delivery may not be appropriate for term breech infants. Therefore, it may be more difficult to find an obstetrician willing to deliver a breech baby without a C-section.

If your baby is in the breech position during the last weeks of pregnancy, you should discuss delivery plans with your doctor and see whether you're a candidate for an external version. If your healthcare provider discovers you have a breech baby during labor itself, you will likely be advised to have a C-section, unless a vaginal delivery seems imminent.