Verbatim from Slate:

Caesarian sections may nearly triple the chance of infant death among low-risk U.S. women, according to a huge study. The death rate is 0.062 percent for vaginal births and 0.177 percent for C-sections.

Speculated reasons: 1) Labor produces hormones that improve babies' lungs. 2) Labor squeezes dangerous fluid from their lungs. 3) C-sections may cause cuts and infections. 4) C-sections delay breastfeeding.

Skeptical reactions: 1) The rest of the world would kill for a neonatal mortality rate under 0.2 percent. 2) The reason C-sections correlate with more deaths is that the riskiest women get C-sections.

Authors' replies: 1) We restricted the study to low-risk women. 2) C-sections correlate with more deaths from multiple causes even after we adjusted the samples for medical factors and socioeconomic status. 3) C-sections are up nearly 50 percent in a decade; maybe we should stop this train. A second, much smaller study suggests that the risk of maternal death is also three times higher in C-sections. (For Human Nature's previous update on births to women over 50, click here.)