Breech Birth Health Article

Definition

In a breech birth, the presenting part of the fetus, or the part that enters the woman's birth canal first, is the buttocks or leg(s).

Description

In almost 97% of vaginal births, the head is the part of the baby to be born first (i.e., vertex presentation). During a woman's pregnancy, the fetus moves freely inside the uterus, cushioned by the amniotic fluid. At 20 weeks' gestation, the midway point in the pregnancy, about 24% of fetuses are in a breech position. By 34 weeks, only about 7% are in a breech position. As the pregnancy progresses towards term (37–42 weeks), the growing fetus has less room in which to turn around, and usually remains more in an inverted (head down) position. However, in about 3–4% of births, the buttocks or feet present first.

There are three types of breech presentations:

• Complete breech, in which the buttocks present first, the baby's thighs are tight against the abdomen, the legs are crossed, and the feet are flexed. In this position, the fetus is curled up tightly in a ball.
• Frank breech, in which the knees are straight (i.e., not bent), and the legs are held tightly against the abdomen and head. This breech position comes closest to filling the pelvic inlet, as would the fetus's head.
• Footling breech, in which one or both legs enter the birth canal first. The fetus appears to be standing in an upright position.

Risks

Risks of a vaginal breech delivery include:

• Prolapse of the umbilical cord. This is especially true in a footling presentation, where the feet and legs are small and provide room for the umbilical cord to slip alongside and into the birth canal. Any pressure on the cord compresses the sides of the cord, decreasing blood flow and oxygen to the fetus. This may result in anoxia.
• Entrapment of the head. This occurs when the body of the neonate passes through the cervix, but the head, which is the largest part of the body, cannot fit through the cervical opening. This may occur because the cervix was incompletely dilated at the time of the birth of the baby, or when the head is larger than the pelvic opening.
• Trauma to the head or neck of the neonate during delivery. This could result in permanent brain damage or paralysis of the infant.
• Trauma to the spine or an arm resulting in fracture of a bone.
• Meconium aspiration. The breech position may cause an early rupture of the amniotic fluid membranes, and meconium (the infant's first stool) may be released. If the neonate breathes in any of the meconium, he or she risks obstruction of the airway by the meconium, and pneumonia.
• Dysfunctional labor. Because of the fetal breech position, the labor can be drawn out, exhausting the mother, and diminishing her ability to push as the time of delivery approaches.
• Higher level of perinatal morbidity and mortality.

Accurate imaging of the fetus in utero has decreased the number of breech births by alerting obstetricians and midwives to this presentation prior to the time of delivery. A technique called external version may be used to encourage the fetus to rotate into a vertex position. This technique will be described below, under "Treatment." However, as the practice of external version has increased, practitioners have had less experience delivering a breech baby vaginally. A successful vaginal delivery of a breech presentation depends to a great extent on the skill and experience of the practitioner.

Twins present a special challenge, and will take one of several possible birth positions:

• Vertex-vertex. In this, the safest of positions for delivery, the twins both present in the vertex, or head down position. It occurs in about 40–45% of twin births.
• Vertex-breech or breech-vertex. This position offers the most efficient use of the uterine space, but is not the best presentation for delivery. Vertex-breech and vertex-transverse positions occur in about 35–40% of twin births. Breech-vertex positioning occurs in about 15–20% of births.
• Breech-breech presentation occurs in about 15-20% of twin births, and almost always results in cesarian-section birth.

If the second twin entering the birth canal is the larger, there will be a concern that he or she may become stuck because the smaller, first twin did not adequately enlarge the cervical opening. Twins are often born prematurely, and are smaller than full-term infant. The more premature the infant, the greater the chance it will have a smaller body-to-head proportion than the full-term infant. This creates a greater hazard for breech birth, because the small body can come through a less-dilated cervix, and there is a greater chance that the head will get trapped. Accurate imaging of twin positions will play a major role in determining the safest delivery method. An external version of the second twin may be proposed. Version of the first twin in unlikely, as the procedure poses a threat to both twins.