Gestational Diabetes Mellitus prevalence and folic acid food fortification: Insights from Australian pregnancy cohorts

Objectives: Gestational diabetes mellitus (GDM) incidence in Australia increased from 5.6% in 2010 to 19.3% in 2022, coinciding with national folic acid (FA) food fortification. High FA intake has been associated with increased insulin resistance and GDM. We examined the association between Australian FA food fortification and maternal folate, placental endocrine function, maternal insulin resistance and GDM incidence.Design and setting: Case control study of two pregnancy cohorts recruited at the same hospital prior to (SCOPE; 2005-2008; Total N=1164) and post (STOP; 2015-2018; Total N=1300) FA food fortification.Outcomes: Circulating folate, red cell folate (RCF), insulin, glucose, prolactin (PRL), human placental lactogen (hPL) and placental growth hormone (GH2) were measured in early pregnancy maternal blood. Results: GDM incidence increased from 5% (SCOPE) to 15.2% (STOP) and was associated with increased maternal folate. Compared to pre-FA fortification, women post-fortification had higher serum folate (18%; p