January 7, 2009

BIRMINGHAM, Ala. - Women choosing repeat cesarean deliveries and having them at 37 or 38 weeks gestation, without a medical or obstetric indication, are up to two times more likely to have a baby with serious complications, including respiratory distress resulting in mechanical ventilation and NICU admission.

UAB researchers, led by Alan T.N. Tita, M.D., Ph.D., assistant professor in the UAB Department of Obstetrics and Gynecology Division of Maternal-Fetal Medicine, and colleagues published their findings Jan. 8 in the New England Journal of Medicine.

"The cesarean rate in the United States has risen dramatically, from 20.7 percent in 1996 to 31.1 percent in 2006. A major reason is the decline in attempted vaginal births after cesarean. Because elective cesareans can be scheduled to accommodate patient and physician convenience, there is a risk that they may be performed earlier than is appropriate." Tita said. "We knew from previous small studies that infants born before 39 weeks gestation are at increased risk for respiratory distress. Because nearly 40 percent of the cesareans performed in the United States each year are repeat procedures, we undertook this large study to describe the timing of elective repeat cesareans and assess its relationship with the risk of various adverse neonatal outcomes."

Tita and colleagues looked at women who had elective repeat cesarean sections at the 19 centers of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Maternal-Fetal Medicine Units Network from 1999 through 2002. They were selected from the network's Cesarean Section Registry. The registry contains detailed, prospectively-collected information on nearly 50,000 women with a prior cesarean who underwent either repeat cesarean delivery or a trial of labor at the 19 centers over the 4-year period. Of the 50,000, 13,258 women underwent an elective cesarean of a viable infant at 37 weeks gestation or later, in the absence of labor or other obstetric or medical indications for early cesarean delivery (prior to 39 weeks).

The researchers looked at whether an infant who was delivered at 37 weeks later died or was diagnosed with a number of conditions, including respiratory distress syndrome and/or transient tachypnea of the newborn, newborn sepsis, seizures, necrotizing entercolitis, hypoxic ischemic encephalopathy, required ventilator support within 24 hours of birth, had umbilical cord arterial pH (a measure of oxygenation) below 7.0, an Apgar score at five minutes of three or below, was admitted to a neonatal intensive care unit or required prolonged hospitalization. 

Of the 13,258 women who had elective repeat cesarean sections, as many as 35.8 percent were delivered before 39 weeks. Babies born at 37 weeks were two times more likely to suffer with conditions common to babies born too soon, and at 38 weeks, they were one and a half times more likely.

Tita said these findings, along with other studies, underscore the importance of not delivering a baby before 39 weeks for the sake of convenience. "Unfortunately, these early deliveries are associated with a preventable increase in neonatal morbidity and NICU admissions, which carry a high personal and economic cost. These findings support recommendations to delay elective delivery until 39 weeks gestation and should be helpful in counseling women on the necessity of waiting to deliver."

UAB is one of the original eight National Institute of Child Health and Human Development (NICHD) research sites commissioned in 1986 and is the only facility in the country that is involved in all three of the NIH research initiatives for maternal, child and family health, the Neonatal Research Network, Maternal-Fetal Medicine Units Network and the Global Network for Women and Children Research. The under-construction, 400,000-square-foot UAB Women and Infants Center, scheduled to open in 2010, will provide medical evaluation and private inpatient rooms for expectant mothers experiencing both normal pregnancies and severe pregnancy-related complications, for both healthy and critically ill newborns and for women undergoing gynecological procedures or treatment for gynecologic cancers.