Association between maternal milk intake during pregnancy and birth size of infants: results from the Japan Environment and Children's Study

Cow milk is rich in essential nutrients for fetal growth. We investigated associations of maternal milk intake and macronutrient intake from milk with birth size.

We included 79,976 mother-infant pairs from an ongoing nationwide prospective Japanese cohort study. Maternal milk intake (full-fat and low-fat milk) was assessed through a food frequency questionnaire. Multiple logistic regression was performed to investigate the associations of total milk intake and macronutrient intake from milk with small for gestational age (SGA) and large for gestational age.

Median total milk intake was approximately 96.9 mL/day during pregnancy. The highest quintile of total milk intake was associated with a decreased SGA risk compared with the lowest quintile of total milk intake (odds ratio: 0.87; 95% confidence interval: 0.80-0.95). Compared with women who consumed full-fat milk less than once per month, women with a higher frequency of full-fat milk intake were less likely to have SGA. No association was observed when the analysis was limited to those who did not consume full-fat milk. Compared with the lowest quintile, the higher quintiles of protein, fat, and carbohydrate intake from milk were associated with a reduced risk of SGA. There were no associations of milk intake with large for gestational age.

We found that milk intake during pregnancy, particularly full-fat milk, was associated with a lower risk of SGA in a cohort of pregnant women with relatively low milk intake. Our results support the hypothesis that milk intake during pregnancy promotes fetal growth.