Long and short interpregnancy interval increases severe maternal morbidity

Abstract Background Severe maternal morbidity (SMM) is a composite variable that includes adverse maternal outcomes during pregnancy that are associated with maternal mortality. Previous literature has shown that inter-pregnancy interval (IPI) is associated with preterm birth, fetal growth restriction and low birth weight, but the association of IPI and composite SMM is not well studied. Objective We sought to determine the relationship between interpregnancy interval (IPI) stratified as Study Design This is a retrospective cohort study of multiparous women 15-54 years old with singleton, non-anomalous births between 23-42 weeks gestation in California (2007-2012). We defined SMM as the composite score of a published list of ICD-9 (International Classification of Diseases, 9th Revision) diagnoses and procedure codes, provided by Center for Disease Control and Prevention (CDC). We used chi-square tests for categorical variables and multivariable logistic regression models were utilized to determine the association of IPI (independent variable) with SMM (dependent variable), adjusted for maternal race/ethnicity, age, education, body mass index, insurance, prenatal care, smoking status and maternal co-morbidity index score. Results In this study, 1,669,912 women met inclusion criteria and of these, 0.87% (n=14,529) of women had SMM and 0.28% (n=4,712) had ntSMM. Multivariable logistic regression models showed that compared to women with 18-23 months IPI, women with IPI of less than 6 months (aOR=1.23; 95% CI: 1.14-1.34) and ≥60 months (aOR=1.11; 95% CI: 1.04-1.19) had significantly higher adjusted odds of SMM. Odds of ntSMM is higher in women with long IPI (≥60 months) after controlling for the same potential confounders (aOR=1.17, 95% CI: 1.04-1.31). We also found significantly higher odds of requiring ventilation (aOR=1.34; 95% CI: 1.03-1.75) and maternal sepsis (aOR=2.08; 95% CI: 1.31-3.31) in women with long IPI. Conclusion Risk of SMM is higher in women with short IPI (