Evaluating pre-pregnancy dietary diversity vs. dietary quality scores as predictors of gestational diabetes and hypertensive disorders of pregnancy.

Background: Dietary diversity scores (DDS) are considered as metrics for monitoring the implementation of the UN's Sustainable Development Goals, but they need to be rigorously evaluated.

Objective: To examine two DDS, the Food Groups Index (FGI), and the Minimum Dietary Diversity-Women (MDD-W), alongside two dietary quality scores, the Alternate Healthy Eating Index (AHEI-2010) and the Prime Diet Quality Score (PDQS), with risks of gestational diabetes mellitus (GDM) and hypertensive disorders of pregnancy (HDPs).

Design: The analysis included 21,312 (GDM) and 19,917 (HDPs) singleton births reported in the Nurses' Health Study II cohort (1991-2001), among women without major chronic disease or GDM/HDPs. Scores were derived using prepregnancy diet collected by a comprehensive food frequency questionnaire. Multivariable models were utilized to calculate relative risks (RR) and confidence intervals (95%CIs).

Results: Incident GDM (n = 916) and HDPs (n = 1,421) were reported. The MDD-W and FGI were not associated with risk of GDM or HDPs, but the AHEI-2010 and PDQS were associated with a lower risk of GDM and marginally lower risk of HDP. The RR's of GDM comparing the highest vs. lowest quintiles were 1.00 (95%CI: 0.79, 1.27; p-trend = 0.82) for MDD-W, 0.96 (95%CI: 0.76, 1.22; p-trend = 0.88) for FGI, 0.63 (95%CI: 0.50, 0.81; p-trend <0.0001) for the AHEI-2010 and 0.68 (95%CI: 0.54, 0.86; p-trend = 0.003) for the PDQS. Similarly, the RR's of HDPs were 0.92 (95%CI: 0.75, 1.12, p-trend = 0.94) for MDD-W, 0.97 (95%CI: 0.79, 1.17; p-trend = 0.83) for FGI, 0.84 (95%CI: 0.70, 1.02; p-trend = 0.07) for AHEI-2010 and 0.89 (95%CI: 0.74, 1.09; p-trend = 0.07) for PDQS.

Conclusions: MDD-W and FGI did not predict the risk of GDM and HDPs. These DDS should not be widely used as metrics for achieving dietary goals in their present form. The Prime Diet Quality Score warrants further testing as a promising measure of a sustainable and healthy diet on a global scale.