Breast milk leptin plays a potential role in preventing childhood obesity. However, the associations of breast milk leptin with maternal metabolism in pregnancy and dietary patterns during lactation are still unclear. We aimed to explore associations of breast milk leptin with maternal metabolic profiles in pregnancy and dietary patterns during lactation. A total of 332 participants were recruited for this retrospective cohort study. Breast milk samples were collected at approximately 6 weeks postpartum. Breast milk leptin and twenty-three metabolic profiles in pregnancy were measured in this study. A semi-quantitative FFQ was used to gather dietary information during lactation. Both principal component analysis and the diet balance index were used to derive dietary patterns. Among twenty-three maternal metabolic profiles, maternal serum glucose (β = 1·61, P = 0·009), γ-glutamyl transferase (β = 0·32, P = 0·047) and albumin (β = −2·96, P = 0·044) in pregnancy were correlated with breast milk leptin. All dietary patterns were associated with breast milk leptin. Given the joint effects of maternal metabolism in pregnancy and dietary patterns during lactation, only diet quality distance was significantly associated with leptin concentrations in breast milk (low level v. almost no diet problem: β = −0·46, P = 0·011; moderate/high level v. almost no diet problem: β = −0·43, P = 0·035). In conclusion, both maternal metabolism in pregnancy and dietary patterns during lactation were associated with breast milk leptin. Maternal diet balance during lactation was helpful to improve breast milk leptin concentration.

This study aimed to describe diet quality of pregnant women and explore the association between maternal diet and the prevalence of low birth weight (LBW) and small for gestational age (SGA). A total of 3856 participants from a birth cohort in Beijing, China, were recruited between June 2018 and February 2019. Maternal diet in the first and second trimesters was assessed by the Chinese diet balance index for pregnancy (DBI-P), using data collected by the inconsecutive 2-d 24-h dietary recalls. Logistic regressions were performed to explore the independent effects of DBI-P components on LBW and SGA. The prevalence of LBW and SGA was 3·8% and 6·0%, respectively. Dietary intakes of the participants were imbalanced. The proportions of participants having insufficient intake of vegetables (87·3% and 86·6%), dairy product (95·9% and 96·7%) and aquatic foods (80·5% and 85·3%) were high in both trimesters. The insufficiency of fruit intake was more severe in the second (85·2%) than that in the first trimester (22·5%) (P < 0·05). After adjusting for potential confounders, the intake of fruits and dairy in the second trimester was negatively associated with the risk of LBW (OR = 0·850, 95% CI: 0·723, 0·999) and SGA (OR = 0·885, 95% CI: 0·787, 0.996), respectively. Sufficient consumption of fruits and dairy products in pregnancy may be suggested in order to prevent LBW and SGA.