Pre-pregnancy dietary micronutrient adequacy is associated with lower risk of developing gestational diabetes in Australian women

Evidence on pre-pregnancy dietary micronutrient intake in relation to gestational diabetes (GDM) development is limited. Therefore, we examined the prevalence of inadequate micronutrient intake before pregnancy and the association between pre-pregnancy dietary micronutrient adequacy, i.e. meeting micronutrient intake recommendations for a range of micronutrients, and risk of developing GDM in an Australian population. We hypothesized that women with an overall higher micronutrient adequacy would have a lower risk of developing GDM. We used data from the prospective Australian Longitudinal Study on Women's Health cohort, in which 3607 women, aged 25-30 years at baseline in 2003 and without diabetes, were followed-up until 2015. Diet was assessed with a validated 101-item food frequency questionnaire. The Micronutrient Adequacy Ratio (MAR) was calculated as the micronutrient intake divided by its recommended dietary intake averaged over 13 micronutrients. Multivariable regression models with generalized estimating equations were used to estimate relative risks (RR) and 95% confidence intervals (95% CI). In 6263 pregnancies, 285 cases of GDM were documented (4.6%). High prevalences of inadequate dietary micronutrient intake were observed for calcium (47.9%), folate (80.8%), magnesium (52.5%), potassium (63.8%) and vitamin E (78.6%), indicating suboptimal pre-pregnancy micronutrient intakes. Inadequate intakes of individual micronutrients were not associated with risk of developing GDM. However, women in the highest quartile of the MAR had a 39% lower risk of developing GDM compared to women in the lowest quartile (RR 0.61, 95% CI 0.43-0.86, p for trend 0.01). These results highlight the importance of adequate pre-pregnancy micronutrient intake.