American Medical Association Family Medical Guide - American Medical Association [301]
Normal presentation
In a normal presentation, the baby’s head is down and facing the mother’s back. This position allows for the easiest passage through the birth canal.
Breech presentation
In a breech presentation, the baby is positioned with the buttocks down, usually with the buttocks against the cervix. Breech presentation is common in cases of preterm labor (see page 529) because the fetus hasn’t had time to assume the normal position for delivery, which usually occurs later in pregnancy. Babies in a breech presentation can often be delivered vaginally (usually with the aid of forceps), but a cesarean (see previous page) is frequently performed to avoid complications.
During the last few weeks of pregnancy, a doctor may be able to manipulate the fetus into the normal presentation using his or her hands on the woman’s abdomen, usually guided by ultrasound. This manual manipulation, called external version, is done only when the baby is mature enough for delivery. If the baby is still in the breech position when labor begins and you have no other problems, your doctor may recommend allowing labor to continue while preparing for a cesarean delivery if labor becomes difficult.
Breech presentation
In a breech presentation, the fetus passes through the birth canal with the head up and either the buttocks or feet against the cervix. A vaginal delivery is possible with a baby in the breech position, but a doctor may use forceps to aid the delivery or perform a cesarean delivery. In a frank breech (left), the baby’s hips are bent and the legs extend upward, toward the head. In a footling breech (center), one or both of the baby’s feet are over (or protrude into) the cervix. In a complete breech (right), both the baby’s hips and knees are bent.
Prolonged Labor
Prolonged labor is defined as labor that lasts longer than 20 hours for a woman’s first delivery and longer than 14 hours for a subsequent delivery. Labor can be prolonged if the muscles of the uterus do not produce sufficiently strong or regular contractions to dilate the cervix. Having epidural or spinal anesthesia (see page 532) can interfere with muscle contraction. In some cases, the fetus’s head is too large to pass through the woman’s pelvis, or the fetus is in an abnormal position that makes delivery difficult.
Your doctor may induce labor (see page 533) by giving you the hormone oxytocin intravenously (through a vein) to stimulate uterine contractions. Depending on the stage of labor and the position of the fetus, your doctor may perform a cesarean delivery (see page 534) or use forceps (see page 534) to assist delivery.
Disproportion
The term disproportion means that the woman’s pelvis is too narrow for the passage of the baby’s head. Disproportion can occur in women of any size or height but is more common in small-boned women and in women who are shorter than 5 feet. In some cases, a woman’s pelvis is disproportionately small because of a previous injury. Disproportion can also occur if the baby’s head is abnormally large, as with babies who have hydrocephalus (see page 400).
If your doctor suspects that your pelvis may be too small for the baby’s head to pass through, he or she will perform an ultrasound of your pelvis. If the disproportion seems severe, the doctor will probably recommend a cesarean delivery (see page 534). If the disproportion is not too severe, he or she may decide to proceed with a vaginal delivery but closely monitor the baby’s condition throughout labor.
Prolapse of the Umbilical Cord
A prolapsed umbilical cord occurs during (and in rare cases before) delivery when the umbilical cord drops down into the cervix or vagina. A compressed cord can cut off the fetus’s blood and oxygen supplies, causing severe damage to or death of the fetus within minutes. A prolapsed cord can occur with conditions such as