Maternal menstrual history and small-for-gestational-age births in a population-based Chinese birth cohort.

The relationship between maternal menstrual history and small-for-gestational-age (SGA) births is examined in a population-based birth cohort of 5291 mothers with singleton births and 28 completed gestational weeks in Qingdao, China, in 1992. Multivariate analyses suggest that the length of the menstrual cycle and age at menarche had independent effects on SGA after controlling for sex of the infant, physical size of the mother, blood pressure at the first antenatal visit, parity, gestational week at the first antenatal visit, number of antenatal visits, number of previous spontaneous abortions and maternal educational attainment and occupation. The relative risk (RR) of SGA among thin mothers (BMI < = 21) is 1.63 (95% confidence interval (CI) 1.16-2.29) if the mother's menarche started after 14 years (reference to < = 14 years), 1.75 (95% CI 0.96-3.20) if the mother's menstrual cycle was 29-30 days and 2.92 (95% CI 1.42-6.03) if the menstrual cycle > = 31 days ( < = 28 as a reference category for both). Among normal weight mothers (BMI 21-24), only a menstrual cycle equal or longer than 31 days still had a significant effect on SGA (RR 2.17, 95% CI 1.18-4.08), and among fat mothers no significant effects were observed. The results encourage further evaluation of the association between maternal menstrual background and fetal development among other ethnic populations and exploration of the possible biological mechanisms behind this relationship.