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

Abstract

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.

Keywords: birth spacing; birth-to-conception interval; interpregnancy interval; perinatal; preterm; review.

Figure 1

Literature flow diagram. *947 records include eight unique records identified from a targeted review conducted on September 22, 2017 to find articles on interpregnancy intervals and uterine rupture, placental abruption and placenta previa, which were outcomes relevant to the maternal outcomes systematic review

Figure 2

A, Adjusted odds ratios and 95% confidence intervals for the association between interpregnancy interval and preterm birth among studies rated as having “good” internal validity from high‐resource settings. Black solid circles indicate the reference category, and red solid circles indicate studies using a sibling comparison design; B, Adjusted odds ratios and 95% confidence intervals for the association between interpregnancy interval and preterm birth among studies rated as having “fair” internal validity from high‐resource settings. Black solid circles indicate the reference category. Confidence intervals are not discernible for some studies because they fell within the range covered by the point estimate symbol (black hollow circle); C, Adjusted odds ratios and 95% confidence intervals for the association between interpregnancy interval and spontaneous preterm birth among studies from high‐resource settings. Black solid circles indicate the reference category

Figure 3

Adjusted odds ratios and 95% confidence intervals for the association between interpregnancy interval and small for gestational age birth among studies from high‐resource settings. Black solid circles indicate the reference category, red solid circles indicate studies using a sibling comparison design, and vertical dashed line separates studies with good internal validity from those with fair internal validity. Confidence intervals are not discernible for some studies because they fell within the range covered by the point estimate symbol (black hollow circle)

Figure 4

A, Adjusted odds ratios and 95% confidence intervals for the association between interpregnancy interval and perinatal death among studies from high‐resource settings. Black solid circles indicate the reference category, and vertical dashed line separates studies with good internal validity from those with fair internal validity; B, Adjusted odds ratios and 95% confidence intervals for the association between interpregnancy interval and infant death among studies from high‐resource settings. Black solid circles indicate the reference category, and vertical dashed line separates studies with good internal validity from those with fair internal validity