(RxWiki News) Women who have had one cesarean section and are planning another should aim for delivering after 39 weeks of pregnancy according to a new study.
Comparing the risks of choosing to have a C section at each week forward starting from the 37th week, a researcher analyzing almost 24,000 repeat C sections found week 39 to be safest for mother and child.
"Schedule C sections for the 39th week of pregnancy."
Dr. Giuseppe Chiossi completed the study for the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), Maternal-Fetal Medicine Units Network in Bethesda, Md.
Chiossi tracked the women who had repeat cesarean sections over four years at 19 different medical centers.
He classified the 23,794 repeat C sections according to whether each was elective or medically necessary and occurred with or without labor.
Then he looked at all the complications that may have occurred for the mother or child in each case.
He found that a lower rate of medical problems with the newborn occurred if women had their babies later than the 37th or 38th week, but then they picked up again from week 40 onward.
Likewise, mothers experienced fewer complications during birth if they waited until after weeks 37 and 38, but outcomes became much worse if they waited past week 39.
Therefore, he concluded, "the optimal timing of elective delivery for mother and baby is 39 weeks, even after consideration of the risk with continuing pregnancy."
These results confirm the findings of similar studies showing fewer adverse outcomes for newborns delivered after 38, according to Dr. Kevin Gordon, M.D., an obstetrician and gynecologist at Omega OBGYN in Arlington, Texas, who was not associated with the study.
"This is not surprising since the additional time allows fetal lung maturation," Gordon told dailyRx. "Therefore elective cesarean sections - ones that do not possess underlying medical conditions - should not take place until 39 weeks."
In mothers, the complications he looked at included pulmonary edema (a build-up of water in the lungs), blood clots, pneumonia, a necessary hysterectomy or an abscess in the pelvis. He also looked at how many women required a blood transfusion or died.
For the infants, Chiossi noted those who had breathing difficulties, infection, extra fluid remaining in the lungs, gastrointestinal disease, seizures and brain damage from lack of oxygen. He also included babies who had under a 3 on the Apgar score, who required NICU care or assisted ventilation, or who died.
Chiossi adjusted his findings to control for the mothers' race and ethnicity, age, weight, medical history, the number of previous C sections they had, their marital status and health insurance status and whether they smoked.
The most common gestational week for the C sections was the 39th week with 41 percent of the women giving birth then, followed by 31 percent of the women having a C section in the 38th week.
Only 5 percent had theirs at 41 weeks or later, and the rest were split between week 37 and week 40.
The study was presented February 10 at the Society for Maternal-Fetal Medicine's annual meeting, The Pregnancy Meeting, in Dallas, TX. The study was funded by the NICHD. Chiossi did not state any conflicts of interest.