While it used to be standard procedure to do a C-section for a mother expecting twins, with the advent of sophisticated ultrasound capabilities, more and more mothers are able to deliver their babies vaginally because the doctors can determine the babies' positions in the womb. The conventional wisdom is that if the first baby is headfirst, that child can be delivered vaginally. If the second baby is breech, the doctor can sometimes manually turn him in the uterus after the first baby is out of the way. Or, if the baby is small enough, he can be delivered breech. About 40 percent of twin pregnancies have at least one of the babies in a breech position, and eight percent have both babies in the breech position, reports Noble.
Further complications can arise if too much time has elapsed between the delivery of the two babies and the cervix has begun to close, or if the second baby is bigger than the first. If the first baby's position presents a problem (if she's not head-first) or there's a concern that the umbilical cords may become tangled, a C-section is usually done.
"Difficult birth positions may sometimes be resolved through manipulation of the babies by the attending practitioners," according to the book Mothering Twins. "Emergency situations that necessitate Cesarean birth may arise during labor after preventative, alternative, or medical techniques have failed. These include fetal distress, prolonged or arrested labor due to ineffective contractions, or to a disproportionate fit of the head/buttocks to the pelvis."
Author Paula Spencer says the situation may be aggravated if the mother's contractions aren't strong enough. "Mothers of twins tend to have slow labors, perhaps because the overstretched uterus doesn't contract as efficiently," she writes in Parenting Guide to Pregnancy and Childbirth. "On the other hand, the cervix has usually begun to dilate before a twin labor starts, which can make things seem to go faster. Twins also tend to be smaller than full-term singletons, making their delivery easier."
The average birth weight for twins is 5 pounds, 5 ounces, compared to 7 pounds, 7 ounces, for single babies, NOMOTC reports, adding that a set of twins can vary in weight by two to three pounds. The interval between the births of twins is usually less than an hour, with five to 10 minutes between starting the delivery of the second baby, the group's website says.