Schummers L, et al. - In this population-based cohort study, researchers determined if the relationship between short interpregnancy (delivery to conception) interval and adverse pregnancy outcomes is modified by maternal age. Findings suggested an association of short interpregnancy intervals with increased risks for adverse pregnancy outcomes for women of all ages.

Methods

• In this investigation conducted in British Columbia, Canada, researchers assessed women with ≥ 2 singleton pregnancies from 2004-2014 with the first (index) pregnancy resulting in a live birth.
• Data analysis was performed from January 1-July 20, 2018.
• Main outcomes and measures analyzed included risks of maternal mortality or severe morbidity, small-for-gestational, fetal and infant composite outcome, and spontaneous and indicated preterm delivery.
• According to maternal age at index birth (20-34 and ≥ 35 years), risks of each outcome for 3- to 24-month interpregnancy intervls were estimated.
• They also calculated adjusted risk ratios comparing predicted risks at 3-, 6-, 9-, and 12-month intervals with risks at 18-month intervals for each age group.
• In several sensitivity analyses, the potential role of other factors explaining any differences (unmeasured confounding) was examined.

Results

• Maternal mortality or severe morbidity risks were increased at 6- vs 18-month interpregnancy intervals for women aged ≥ 35 years but not for women aged 20-34 years among 148,544 pregnancies.
• Compared with women aged ≥ 35 years, increased adverse fetal and infant outcome risks were more pronounced for women aged 20-34 years.
• Findings revealed that risks of spontaneous preterm delivery at 6-month interpregnancy intervals were increased for women aged 20-34 years and, to a lesser extent, for women aged ≥ 35 years.
• It was noted that modest increases in risks of small-for-gestational age and indicated preterm delivery at short intervals did not differ meaningfully by maternal age.
• According to sensitivity analyses, observed associations were not fully explained by unmeasured confounding.