Background: Although low birth weight in Japan has slightly increased over the past several decades, the association between maternal birth weight and pregnancy outcomes remains poorly understood.
Methods: In this hospital-based, prospective cohort study conducted at the National Center for Child Health and Development, we obtained information on pregnant women's birth weight via their maternal and child health handbook. We analyzed 944 women born at term after dividing them into five categories according to their birth weight: <2500 g, 2500-2999 g, 3000-3499 g, 3500-3999 g, and ≥4000 g. Multivariate logistic regression analysis and trend analysis were used to elucidate the extent to which maternal birth weight was associated with small-for-gestational-age and low birth weight in offspring, as well as with hypertensive disorders of pregnancy.
Results: Compared with women with a birth weight of 3000-3499 g, those born with a birth weight <2500 g had a significantly higher risk of low birth weight (adjusted odds ratio: 5.39, 95% confidence interval: 2.06-14.1) and small-for-gestational-age (adjusted odds ratio: 9.11, 95% confidence interval: 3.14-26.4) infants. No significant association was found between the incidence of hypertensive disorders of pregnancy and preterm birth. A linear relationship was observed between the lower birth weight categories and a higher risk of low birth weight and small-for-gestational-age (p-values for trends: 0.009 and <0.001, respectively), but no linear relationship was observed for the risk of preterm birth and hypertensive disorders of pregnancy (p-value for trends: 0.317 and 0.157, respectively).
Conclusions: Our findings suggest that lower maternal birth weight is associated with small-for-gestational-age and low birth weight in offspring of women born at term.