According to a study published Wednesday in The New England Journal of Medicine if a repeated elective Caesarean delivery is performed before 39th week of pregnancy, the baby's risk of serious respiratory problems and other complications increases by 50% or more.

"Elective Caesarean delivery may be scheduled to accommodate patient and physician convenience, and here is a risk that it may be performed earlier than is appropriate," the authors said.

"This [study] allows us to know how many elective scheduled C-sections are performed before 39 weeks, "said Dr. Catherine Y. Spong, one of the study author's and chief of the Pregnancy and Perinatology Branch of the National Institutes of Health.  "This study is telling us that over one-third of women are having elective repeat Caesareans -- that's not an insubstantial number."

In the study researchers collected data from 19 centers participating in an NIH fetal medicine network and tracked 24,077 women who had repeat C-sections performed between 1999 and 2002. Of these 13,258 women had elective procedures which were performed before 39 weeks of gestation of which 35.8 % were before 39 weeks of gestation.

The researchers noted that neonatal death, respiratory complications, treated hypoglycemia, newborn sepsis, and admission to a neonatal ICU were some of the problems faced in such cases. Alan Tita, M.D., of the University of Alabama at Birmingham, and colleagues noted that a repeat elective Caesarean at 38 weeks was associated with an odds ratio of 1.5 for adverse outcomes, which increased to 2.1 for Caesarean delivery at 37 weeks.

"These early deliveries are associated with a preventable increase in neonatal morbidity and admissions to the neonatal ICU, which carry a high economic cost," the authors said. "These findings support recommendations to delay elective delivery until 39 weeks of gestation and should be helpful in counseling."

The study finds that having a baby by C-section two weeks, or even three or four days, before the 39th week increases the risk of complications for the baby. It also found that having the baby after 40 weeks also increased the risks for bad outcomes.
The authors noted that they "also observed a higher risk of neonatal complications with Caesarean delivery at 41 weeks or later although the overall proportion of mothers delivering this late was small (<5%)."

"Theses findings suggest that in addition to the risk of stillbirth, which is almost doubled at 41 weeks of gestation and increased by a factor of up to five at 42 or more weeks as compared with 39 weeks, the risk of neonatal complications may also be increased by delaying elective Caesarean delivery beyond 39 or 40 completed weeks of gestation."

The study was supported by the National Institute of Child Health and Human Development.