(Medical Xpress)—Infants born to mothers attempting to deliver vaginally before the 32nd week of pregnancy are as likely to survive as those delivered by a planned cesarean, provided the fetus is in the head-first position, according to researchers at the National Institutes of Health.
Pregnancy typically lasts about 40 weeks. Infants born before the 37th week of pregnancy are classified as preterm, and those born before the 32nd week of pregnancy are classified as early preterm. Preterm infants are at risk for a number of health problems, including increased risk of infant death, cerebral palsy, developmental delays, infection and vision and hearing problems. According to the Centers for Disease Control and Prevention, 54 percent of all infant deaths in the United States occur among the 2 percent of infants born before the 32nd week of pregnancy.
Some studies have suggested that infants delivered vaginally before 32 weeks are less likely to survive through infancy than those delivered by a planned cesarean delivery, and more likely to suffer injury and health effects after passing through the birth canal. Cesarean delivery, especially in the early preterm period, poses risks for the mother, such as hemorrhage, bladder injury, and other complications. Women who undergo cesarean delivery are at risk for rupture of the uterus during labor and other complications in subsequent pregnancies.
For the current study, the researchers compared nearly 3,000 women who attempted to deliver vaginally to those who had delivered by a planned cesarean delivery because of a health risk to the mother or baby occurring before 32 weeks requiring delivery. For the fetus in the head first position, the success rate for attempted vaginal delivery was high; 84 percent of women delivered vaginally. Infants in the head-first position were as likely to survive after an attempted vaginal delivery as those delivered by planned cesarean delivery.
However, when the fetus was positioned feet-first (breech presentation), survival rates for deliveries before 32 weeks were considerably higher among infants delivered by planned cesarean delivery, the researchers found.
"The decision to deliver vaginally or by cesarean is an individual one, and must be made carefully by the woman, in close consultation with her physician," said Uma M. Reddy, M.D., M.P.H., of the Pregnancy and Perinatology Branch of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), the NIH institute where the study was conducted. "Our study provides important information for women who are at risk for early preterm delivery and their physicians to take into account when making their decision."
Dr. Reddy conducted the research with NICHD colleagues Jun Zhang, M.D., Ph.D., Liping Sun, M.D., Zhen Chen, Ph.D., Tonse N.K. Raju, M.D., and S. Katherine Laughon, M.D.,. Dr. Zhang is also affiliated with Shanghai Jiaotong University in China.
Their findings appear online in the American Journal of Obstetrics and Gynecology.
The researchers analyzed data from the NICHD Consortium on Safe Labor, a long-term study of labor and delivery practices conducted and supported by the NICHD.
Nearly 80 percent of the women with a fetus positioned head-first attempted a vaginal delivery, and 84 percent of them were successful. The remainder ultimately delivered by cesarean. Of the breech pregnancies, about 30 percent of women attempted vaginal delivery and, depending on the gestational age, between 17 and 28 percent were successful.
"The next step for our research is to further understand adverse outcomes associated with extremely preterm delivery and to determine what long-term neurological and physical disabilities may be associated with these deliveries," Dr. Reddy said.