Short interpregnancy intervals and adverse perinatal outcomes in high‐resource settings: An updated systematic review

BACKGROUND: This systematic review summarises association between short interpregnancy intervals and adverse perinatal health outcomes in high‐resource settings to inform recommendations for healthy birth spacing for the United States. METHODS: Five databases and a previous systematic review were searched for relevant articles published between 1966 and 1 May 2017. We included studies meeting the following criteria: (a) reporting of perinatal health outcomes after a short interpregnancy interval since last livebirth; (b) conducted within a high‐resource setting; and (c) estimates were adjusted for maternal age and at least one socio‐economic factor. RESULTS: Nine good‐quality and 18 fair‐quality studies were identified. Interpregnancy intervals <6 months were associated with a clinically and statistically significant increased risk of adverse outcomes in studies of preterm birth (eg, aOR ≥ 1.20 in 10 of 14 studies); spontaneous preterm birth (eg, aOR ≥ 1.20 in one of two studies); small‐for‐gestational age (eg, aOR ≥ 1.20 in 5 of 11 studies); and infant mortality (eg, aOR ≥ 1.20 in four of four studies), while four studies of perinatal death showed no association. Interpregnancy intervals of 6‐11 and 12‐17 months generally had smaller point estimates and confidence intervals that included the null. Most studies were population‐based and few included adjustment for detailed measures of key confounders. CONCLUSIONS: In high‐resource settings, there is some evidence showing interpregnancy intervals <6 months since last livebirth are associated with increased risks for preterm birth, small‐for‐gestational age and infant death; however, results were inconsistent. Additional research controlling for confounding would further inform recommendations for healthy birth spacing for the United States.