The effects of maternal characteristics and pregnancy status on birth weights

Abstract

Objective: To evaluate the effects of maternal characteristics and pregnancy status on birth weights. Methods: A merged file of birth certificates and household registration for 2001 in Taiwan was used. Samples with singleton births, birth weight between 500-4800 g, gestational age between 20-42 weeks, and maternal age between 10-50 years were included in the analysis. A quantile regression based on Koenker and Bassett (1978) was employed; the results were compared with those obtained by OLS. Results: After adjustment for confounding variables, gestational age, maternal education, and marital status were not significantly correlated with birth weight at any quantile. However, maternal age, maternal medical history, gestational age, and newborn sex were significantly correlated with birth weight at every quantile. Conclusions: When birth weight is expected to be high, OLS is likely to underestimate the impact of maternal age, maternal medical history, and newborn sex, but when birth weight is expected to be low, OLS is likely to overestimate the impact of these factors.