Public release date: 11-Dec-2007

Risk of respiratory morbidity in term infants delivered by elective Caesarean section: a cohort study BMJ Online First

Babies delivered by elective caesarean section around term carry up to a fourfold increased risk of breathing problems compared with babies delivered vaginally or by emergency caesarean section, concludes a study from Denmark published on bmj.com today.

The rate of delivery by elective caesarean section is increasing. Previous studies have shown that elective caesareans are linked to an increased risk of newborn respiratory problems.

The exact reasons for this are unknown, but one explanation is that hormonal and physiological changes associated with labour are necessary for lungs to mature and that these changes may not be present in infants delivered by elective caesarean section. Gestational age at the time of elective caesarean section may also be important.

This risk increased the earlier the caesarean was performed. A nearly fourfold increased risk was found at 37 weeks gestation, a threefold increase in risk at 38 weeks gestation, and a doubling of risk in infants delivered at 39 weeks gestation. Adjusting for maternal factors had little effect.

For example, at 37 weeks, 2.8% of infants delivered by intended vaginal delivery had general respiratory problems compared to 10% of infants delivered by elective caesarean section. At 38 weeks, the proportion was 1.7% compared to 5.1% and at 39 weeks, 1.1% compared to 2.1%.

Analyses after restriction to low risk pregnancies revealed slightly smaller risk estimates at 37 weeks gestation but essentially unchanged estimates at 38 and 39 weeks gestation for serious respiratory problems, whereas the estimates remained unchanged at all gestational ages for general respiratory problems.

They suggest that a significant reduction in neonatal respiratory morbidity may be obtained if elective caesarean section is postponed until 39 completed weeks of gestation.