A few useful studies provide reassurances regarding exposures in the prenatal period and perinatal period that we should NOT worry about.

CN Bernstein et al. Clin Gastroenterol Hepatol 2016; 14: 50-7.

In this study with 1671 individuals with inflammatory bowel disease and 10,488 controls, “people with IBD were not more likely to have been born by cesarean section than controls or siblings without IBD.  These findings indicate that events of the immediate postpartum period that shape the developing intestinal microbiome do not affect risk for IBD.”

J Julvez et al. Am. J. Epidemiol. (2016) Full Text Link: doi: 10.1093/aje/kwv195. First published online: January 5, 2016 (thanks to Mike Hart for this reference)

For parents of autistic kids who avoid fish, this article provides information indicating that this is counter-productive.  ” Seafood consumption during pregnancy is thought to be beneficial for child neuropsychological development, but to our knowledge no large cohort studies with high fatty fish consumption have analyzed the association by seafood subtype.” The authors “evaluated 1,892 and 1,589 mother-child pairs at the ages of 14 months and 5 years, respectively, in a population-based Spanish birth cohort established during 2004–2008…” Key finding: “Consumption of large fatty fish during pregnancy presents moderate child neuropsychological benefits, including improvements in cognitive functioning and some protection from autism-spectrum traits.”

My take: We often worry about the wrong things.  These articles provide reassurance that mode of birth and consumption of seafood during pregnancy are things we should not worry about.