Interpregnancy interval and prevalence of selected birth defects: A multistate study

Background Both short and long interpregnancy intervals (IPIs) have been associated with adverse birth outcomes. We undertook a multistate study to describe the prevalence of selected birth defects by IPI. Methods We obtained data from nine population‐based state birth defects registries for singleton live births in 2000–2009 among mothers with a previous live birth identified through birth certificates. IPI was calculated as the difference between prior birthdate and start of the current pregnancy (conception date). We estimated prevalence of selected defects per 10,000 live births and prevalence ratios (PRs) with 95% confidence intervals (CIs) overall and stratified by maternal age at previous birth and race/ethnicity. Primary analyses focused on short IPI