Caesarian section (C-section) deliveries of full-term babies performed before 39 weeks gestation pose health risks, a new study shows. While 37 weeks gestation is considered full-term, the study provides evidence that babies born by C-section at 37 or 38 weeks face an increased risk of complications including breathing problems, infections, and low blood sugar and are more likely to need intensive care. Due dates are set at 40 weeks gestation.

While the American College of Obstetricians and Gynecologists (ACOG) guidelines state that C-sections are safest after 39 weeks of gestation, the operation is commonly performed electively at 37 or 38 weeks. At this stage, mothers may grow tired of being pregnant and want an early C-section, or they may wish to avoid scheduling conflicts and ensure that their personal doctor is able to perform the surgery.

The study, published in Thursday’s edition of the New England Journal of Medicine, examined a C-section registry from 19 academic medical centers to determine how many C-sections were being performed before 39 weeks and the consequences of such early deliveries. The researchers focused on 13,258 women who had a single child by planned Caesarian after having previously given birth by C-section. They excluded cases where C-section was performed because of medical necessity.

The results showed that more than one-third of Caesarians were performed before the fetus had reached 39 weeks gestation. While 8 percent of babies delivered at 39 weeks had some type of complication, 15 percent of babies delivered by C-section at 37 weeks had complications, meaning these babies were almost twice as likely to experience health problems have as babies delivered at 39 weeks. Babies delivered at 38 weeks were 50 percent more likely to experience complications.

The biggest difference was in breathing problems, with babies born at 37 weeks having four times the rate of these problems compared to 39-week babies. In general, babies born by C-section have a higher risk of breathing difficulties than those born vaginally because they miss out on the labor process that helps clear the lungs of fluid.

The risk of complications also increased for births after 41 weeks, leaving a relatively narrow two-week period surrounding the due date as the optimal time to have a C-section. The study did not include the risk of fetal death that might occur while delaying a C-section until week 39, a figure estimated to be 1 in 1000.

The rate of Caesarian sections in the United States has climbed to 31 percent of all births, an all-time high. Several factors have contributed to the rise including older mothers, higher numbers of multiple births, maternal preference, and the risks of having a vaginal birth after a previous C-section.

If you are considering having an elective C-section, the study suggests that the safest time to schedule the procedure is anytime between 39 weeks, 0 days gestation and 40 weeks, 6 days gestation. If you have been counseled to have a C-section earlier than 39 weeks due to complications such as gestational diabetes, the risk of waiting until 39 weeks likely outweighs any benefits. However, if you are planning your C-section at 37 or 38 weeks for convenience, you may want to talk to your doctor about the costs and benefits of holding off until you reach 39 weeks gestation.

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_{Photo: *clarity*, Flickr, Creative Commons}