Interpregnancy interval and subsequent perinatal outcomes among women delaying initiation of childbearing.

AIM

While delayed initiation of childbearing is associated with adverse perinatal outcomes, whether or not risk persists and whether interpregnancy interval (IPI) affects the subsequent pregnancy remains unclear.

OBJECTIVES

To examine second-pregnancy perinatal outcomes for women initiating childbearing age > or = 30 compared to those initiating childbearing aged 20-29, specifically examining the distribution of adverse perinatal outcomes, and their associations with the interpregnancy interval.

METHODS

Retrospective cohort study using the Missouri maternally linked files 1978-1997. Perinatal outcomes included fetal death, low birthweight, preterm birth and small-for-gestational age. Predictor variables included maternal age at first pregnancy and IPI between the first and second pregnancy.

RESULTS

With an increasing maternal age at first pregnancy, rates of very low birthweight (P = 0.0095), preterm delivery (P = 0.0126), moderately preterm (P = 0.0458), and extremely preterm (P = 0.0008) in the second pregnancy increased, while the rate of small-for-gestational age (P < 0.0001) declined. Interpregnancy intervals <6 and > or = 60 months were associated with a higher rate of adverse outcomes after controlling for maternal age at first pregnancy. Intervals of 12-17 months had the lowest rate of adverse outcomes for mothers 35+. Maternal age > or = 35 years at first pregnancy and IPI <6 months were independent risk factors for an adverse outcome in the second pregnancy, however no statistical interaction between these factors was observed.

CONCLUSION

Delayed initiation of childbearing is associated with a persistent risk of adverse perinatal outcomes in the second pregnancy, with a short IPI contributing to this risk. As numbers of women delaying childbearing beyond age 30 increase, providers should consider these risks in counseling women about their reproductive plans.