Inter-pregnancy interval and pregnancy outcomes among women with delayed childbearing: protocol for a systematic review.

BACKGROUND: Women in high resource nations are increasingly delaying childbearing until their thirties. Delayed childbearing poses challenges for the spacing of a woman's pregnancies. Inter-pregnancy intervals <12 months are associated with risk for adverse pregnancy outcome, yet increased maternal age at delivery is linked with increased risk. The optimal inter-pregnancy interval for older mothers is uncertain. This systematic review will aim to assess the relation between inter-pregnancy interval and perinatal and maternal health outcomes in women who delay childbearing to age 30 and older.

METHODS: We will search MEDLINE, CINAHL, and EMBASE databases for peer-reviewed articles on the effects of inter-pregnancy interval on perinatal and maternal health outcomes among women over 29 years at the time of first birth, in high-income countries. To assess the quality of studies, the Cochrane's Collaboration tool for assessing risk of bias will be used for randomized controlled trials, and the Newcastle-Ottawa tool to assess quality of case control and cross-sectional studies. The quality of the findings on each outcome will be assessed across studies, using the GRADE approach. The decision to conduct meta-analyses will be based on the concordance in definitions used for inter-pregnancy intervals, age groups studied, or outcomes measured among selected studies. We will report odds ratios and/or relative risks and/or risk differences for different inter-pregnancy intervals and perinatal and maternal outcomes as well as pregnancy complications.

DISCUSSION: This systematic review will summarize existing data on the relation between inter-pregnancy interval and perinatal and maternal health outcomes among women who delay childbearing to age 30 and older. Findings will inform clinical best practices to assist mothers over age 30 to space their pregnancies appropriately.

SYSTEMATIC REVIEW REGISTRATION: Prospero CRD42015019057.