Interpregnancy Interval and Severe Maternal Morbidity in Iowa, 2009 to 2014

Maternal mortality and morbidity rates have risen significantly, yet little research has focused on how severe maternal morbidity (SMM) is associated with future reproductive health, such as birth spacing or the likelihood of subsequent SMM. This study focuses on the risk of SMM recurrence and the association of interpregnancy intervals with SMM.

This population-based, retrospective cohort study used Iowa hospital discharge data longitudinally linked to birth certificate data between 2009 and 2014. To examine recurrence of SMM, crude and adjusted multivariable logistic regression models were generated. The associations between varying interpregnancy intervals and subsequent SMM were examined. Crude, stratified, and adjusted risk ratios and their associated 95% confidence intervals were estimated.

A total of 36,190 women were included in this study. Women with SMM in the index delivery had significantly higher odds of SMM in the subsequent delivery (adjusted odds ratio, 8.16; 95% confidence interval, 5.45-12.24) compared with women without SMM. Women with an interpregnancy interval of less than 6 months compared with 18 months or longer were more likely to experience SMM during their subsequent delivery, although the difference was not statistically significant (adjusted odds ratio, 1.41; 95% confidence interval, 0.99, 2.03).

This study demonstrates that women who experience SMM are at markedly increased risk of subsequent SMM. Further investigation is necessary to inform optimal interpregnancy interval recommendations based on prior maternal health outcomes.