Researchers in the US found that compared with deliveries at or after 39 weeks, elective repeat cesareans carried out before 39 weeks of gestation were linked to higher risk of the baby having serious complications, including respiratory distress requiring mechanical ventilation and admission to the NICU.
The study was the work of Dr Alan T.N. Tita, assistant professor at the University of Alabama at Birmingham (UAB) Department of Obstetrics and Gynecology Division of Maternal-Fetal Medicine, and colleagues and is published online on January 8 in the New England Journal of Medicine, NEJM.
For the study, Tita and colleagues studied records of 13,258 women who had elective repeat cesarean sections between 1999 and 2002 at 19 university-based clinical centers belonging to the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Maternal-Fetal Medicine Units (MFMU) Network.
They selected the women from the Cesarean Section Registry of the MFMU network, which contained data on nearly 50,000 women who had already had one cesarean and had either a repeat cesarean or a trial of labor in an MFMU network center over the 4 years of the study. The records they selected were only of women who had an elective cesarean of a viable infant at 37 weeks or later, without other indications for early cesarean delivery (eg labor or other obstetric or medical indications) before 39 weeks.
From the selected records, Tita and colleagues looked to see whether babies delivered at 37 weeks later died or were diagnosed with conditions such as respiratory distress syndrome and/or transient tachypnea of the newborn, seizures, necrotizing entercolitis, newborn sepsis, and hypoxic ischemic encephalopathy.
They also looked at whether the babies had required ventilator support during their first 24 hours of birth, had an umbilical cord arterial pH below 7.0 (was there enough oxygen in their bloodstream during birth), an Apgar score at five minutes of three or below (this assesses general health including reflexes, breathing and muscle tone), were admitted to NICU (neonatal intensive care unit), or needed longer than usual hospitalization.
The results showed that of the 13,258 women who had elective repeat cesarean sections, 35.8 per cent were delivered before 39 weeks.
Infants born at 37 weeks were two times more likely to have conditions common to babies born too soon, and infants born at 38 weeks, were 1.5 times more likely.
Tita said these results, which corroborate those of other studies, emphasize the 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,” said Tita.
“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,” he added.
In the ten years from 1996 to 2006, the rate of cesarean births in the US has risen from 20.7 to 31.1 per cent. Tita said that because this type of delivery can be “scheduled to accommodate patient and physician convenience”, it introduces the risk that it might be performed earlier than is appropriate:
“We knew from previous small studies that infants born before 39 weeks’ gestation are at increased risk for respiratory distress,” said Tita.
“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,” he explained.
“Timing of Elective Repeat Cesarean Delivery at Term and Neonatal Outcomes.”
Tita, Alan T.N., Landon, Mark B., Spong, Catherine Y., Lai, Yinglei, Leveno, Kenneth J., Varner, Michael W., Moawad, Atef H., Caritis, Steve N., Meis, Paul J., Wapner, Ronald J., Sorokin, Yoram, Miodovnik, Menachem, Carpenter, Marshall, Peaceman, Alan M., O’Sullivan, Mary J., Sibai, Baha M., Langer, Oded, Thorp, John M., Ramin, Susan M., Mercer, Brian M., the Eunice Kennedy Shriver NICHD Maternal-Fetal Medicine Units Network.
N Engl J Med Volume 360, No 2, pages 111-120, published online 8 January 2009.
Sources: NEJM, University of Alabama at Birmingham.
Written by: Catharine Paddock, PhD