Maternal diet plays a critical role in epigenetic changes and the establishment of the gut microbiome in the fetus, which has been associated with weight outcomes in offspring. This study examined the association between maternal diet quality before pregnancy and childhood body mass index (BMI) in offspring. There were 1936 mothers with 3391 children included from the Australian Longitudinal Study on Women's Health (ALSWH) and the Mothers and their Children's Health (MatCH) study. Maternal dietary intakes were assessed using a semi-quantitative and validated 101-item food-frequency questionnaire (FFQ). The healthy eating index (HEI-2015) score was used to explore preconception diet quality. Childhood BMI was categorized as underweight, normal, overweight, and obese based on sex and age-specific BMI classifications for children. Multinomial logistic regression with cluster-robust standard errors was used for analyses. Greater adherence to maternal diet quality before pregnancy was associated with a lower risk of offspring being underweight after adjustment for potential confounders, highest vs. lowest quartile (relative risk ratio (RRR) = 0.68, 95% confidence interval (CI): 0.49, 0.96). Higher adherence to preconception diet quality was also inversely linked with the risk of childhood obesity (RRR = 0.49, 95% CI: 0.24, 0.98). This association was, however, no longer significant after adjusting for pre-pregnancy BMI. Sodium intake was significantly associated with decreased risk of childhood overweight and obesity (RRR = 0.18, 95% CI: 0.14, 0.23) and (RRR = 0.21, 95% CI: 0.17, 0.26), respectively. No significant association was detected between preconception diet quality and offspring being overweight. This study suggests that better adherence to maternal diet quality before pregnancy is associated with a reduced risk of childhood underweight and obesity.
Keywords: diet quality; healthy eating index-2015; obesity; offspring; preconception; underweight.