Quantifying the mediating effect of body mass index in the relationship between a Mediterranean diet and development of maternal pregnancy complications: Australian Longitudinal Study on Women’s Health

Background: The contribution of body mass index (BMI) to the observed associations between dietary patterns and risk of gestational diabetes mellitus (GDM) and hypertensive disorders of pregnancy (HDP) remains unclear. Objective: The objective of this study was to formally quantify the mediating effect of prepregnancy BMI in these associations. Design: Women (aged 25–30 y) participating in the Australian Longitudinal Study on Women’s Health were not pregnant at baseline in 2003 and reported ≥1 pregnancy up to 2012. GDM and HDP diagnoses were self-reported for each pregnancy and validated in a subset. A Mediterranean diet score was created by use of a baseline-validated food-frequency questionnaire and dichotomized to reflect low adherence (