Menstrual cycle length and adverse pregnancy outcomes among women in Project Viva

Abstract

Background: Retrospective studies suggest that menstrual cycle length may be a risk marker of adverse pregnancy outcomes, but this evidence is susceptible to recall bias.

Objective: To evaluate the prospective association between menstrual cycle length and the risk of adverse pregnancy outcomes.

Methods: Secondary analysis of 2046 women enrolled in Project Viva at ~10 weeks of gestation and followed through delivery. The exposure was menstrual cycle length. The outcomes included gestational glucose tolerance (gestational diabetes/impaired glucose tolerance [GDM/IGT] and isolated hyperglycaemia), hypertensive disorders of pregnancy (gestational hypertension/preeclampsia), gestational weight gain, birthweight-for-gestational age z-scores (BWZ) categorised in tertiles, preterm birth and birth outcome (live birth and pregnancy loss). We used modified Poisson and multinomial logistic regression adjusted for age, race/ethnicity, parity, age at menarche and pre-pregnancy body mass index.

Results: Mean (SD) age at enrolment was 32.1 (4.9) years. Most women (74.3%) had a cycle length of 26-34 days (reference group), 16.2% reported short cycles (≤25 days), and 9.5% reported long/irregular cycles (≥35 days/too irregular to estimate). Compared with the reference group, women with short cycles had lower odds of GDM/IGT (odds ratio [OR] 0.50, 95% confidence interval [CI] 0.28, 0.89), whereas women with long/irregular cycles had higher odds (OR 1.72, 95% CI 1.04, 2.83). Additionally, women with short cycles had higher odds of having a newborn in the lowest tertile of BWZ (OR 1.45, 95% CI 1.06, 1.98). There was a U-shaped relation between cycle length and preterm birth with both short (relative risk [RR] 1.49, 95% CI 0.98, 2.27) and long/irregular (RR 2.04, 95% CI 1.30, 3.20) cycles, associated with a higher risk.

Conclusions: Variation in menstrual cycle length may be a risk marker of GDM/IGT, lower birth size and preterm birth and flag women who may benefit from targeted monitoring and care before and during pregnancy.

Keywords: adverse pregnancy outcome; birth size; gestational diabetes mellitus; impaired glucose tolerance; menstrual cycle length; preterm birth.