Caesarean section before 39 weeks raises risk to infant lungs, study shows

SAN ANTONIO (Jan. 9, 2009) — For a healthy mother and baby, scheduling a Caesarean section delivery one to two weeks earlier than necessary slightly raises the risk of respiratory and other preventable problems in the newborn, and women should be counseled with this in mind.

That’s the conclusion of a federally funded study conducted at 19 maternal-fetal medicine sites including The University of Texas Health Science Center at San Antonio. The study, sponsored by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), is reported in the Jan. 8 issue of The New England Journal of Medicine.

Between 1999 and 2002, the NICHD Maternal-Fetal Medicine Units Network examined infant health outcomes from Caesarean deliveries performed on an elective basis before 39 weeks of gestation. In healthy mothers and infants, the standard of care recommended by the American College of Obstetricians and Gynecologists is not to deliver by Caesarean until 39 weeks to avoid infant breathing problems, unless an amniocentesis is performed to prove lung maturity.

“But elective Caesarean deliveries are often scheduled prior to 39 weeks for logistical reasons, generally a date for the surgery that is mutually acceptable to the patient and the physician,” said Deborah L. Conway, M.D., associate professor in the Division of Maternal-Fetal Medicine in the UT Health Science Center’s Department of Obstetrics and Gynecology. A former Health Science Center faculty member, Oded Langer, M.D., is a co-author of the NICHD study.

“There are certainly reasons that some women should be delivered after term is achieved (37 weeks) without waiting until 39 weeks,” Dr. Conway said. “These reasons include high blood pressure, diabetes or any concern about the well-being of the fetus.”

The authors carefully omitted from their analysis any women with such problems, leaving only those who probably could have waited until 39 weeks for delivery. “Therefore, the findings of this study are very important because, although the adverse outcomes in the babies were quite rare, they likely could have been prevented by scheduling the deliveries according to the American College of Obstetricians and Gynecologists recommendations,” Dr. Conway said.

The team studied more than 24,000 repeat Caesarean deliveries performed at the 19 centers, including San Antonio’s. The primary study outcome was defined as a composite of neonatal death, respiratory problems, hypoglycemia (low blood sugar), newborn sepsis (blood infection) and intensive care unit admission.

More than half of the deliveries were performed electively (13,258). Of those, 35.8 percent were performed before 39 weeks of gestation (6.3 percent at 37 weeks and 29.5 percent at 38 weeks). One neonatal death occurred, but it was in an infant born at 39 weeks. Births at 37 weeks and 38 weeks were associated with an increased risk of the primary study outcome.

In the paper’s opening section, the authors noted that “the rate of Caesarean delivery in the United States rose from 20.7 percent in 1996 to 31.1 percent in 2006.” Because this trend is continuing and increasing, they wrote, “the timing of elective Caesarean delivery has increasingly important public health implications.”

The University of Texas Health Science Center at San Antonio is the leading research institution in South Texas and one of the major health sciences universities in the world. With an operating budget of $668 million, the Health Science Center is the chief catalyst for the $15.3 billion biosciences and health care sector in San Antonio’s economy. The Health Science Center has had an estimated $35 billion impact on the region since inception and has expanded to six campuses in San Antonio, Laredo, Harlingen and Edinburg. More than 23,000 graduates (physicians, dentists, nurses, scientists and other health professionals) serve in their fields, including many in Texas. Health Science Center faculty are international leaders in cancer, cardiovascular disease, diabetes, aging, stroke prevention, kidney disease, orthopaedics, research imaging, transplant surgery, psychiatry and clinical neurosciences, pain management, genetics, nursing, dentistry and many other fields. For more information, visit

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