The association between prepregnancy dietary fatty acids and risk of gestational diabetes mellitus: A prospective cohort study

Background & aims: Epidemiologic studies have examined the association between dietary fatty acids and type 2 diabetes risk in general populations. Evidence regarding their associations with gestational diabetes mellitus (GDM) risk remains limited. This study aimed to evaluate prepregnancy fatty acids intake in relation to GDM risk. Methods: 3,725 pregnant women from the Xi'an Birth Cohort Study who were free of previous GDM or pre-existing chronic diseases were included. Dietary intake of total fat and individual fatty acids (including saturated fatty acids [SFA], monounsaturated fatty acids [MUFA], polyunsaturated fatty acids [PUFA], and trans fatty acids) during the year preceding pregnancy was assessed by a validated food-frequency questionnaire before 16 weeks of gestation. GDM was confirmed based on the 75-g oral glucose tolerance test. Log-binomial or modified Poisson regression models were applied to estimate the relative risks (RRs) and 95 % confidence intervals (95%CIs) of GDM for fatty acids intake. Generalized linear regression was adopted for blood glucose levels with fatty acids intake. Results: 644 (17.3 %) incident GDM cases were confirmed in our study. Participants in the highest intake of total fat substituting for carbohydrates had a 33 % reduced risk of GDM than those in the lowest intake (RR:0.67; 95%CI:0.55,0.81). For individual fatty acids, only PUFA intake was associated with a lower risk of GDM, with RR comparing extreme tertiles of 0.61 (95%CI:0.49,0.76). Each 2 % increase in energy from total fat and PUFA replacing carbohydrates decreased the risk of GDM by 6 % (95%CI:3 %,9 %) and 15 % (95%CI:9 %,21 %), respectively. Similar inverse associations with intake of total fat and PUFA were observed for blood glucose levels. Further analyses of SFA substitution showed that replacement of 2 % energy from SFA with PUFA and MUFA was associated with 26 % (RR:0.74; 95%CI:0.62,0.88) and 30 % (RR:0.70; 95%CI:0.50, 0.98) decreased risk of GDM, respectively. Conclusions: Greater intake of total fat and PUFA before pregnancy was associated with lower risk of GDM when replacing carbohydrates. Substitution SFA with PUFA and MUFA was also inversely associated with GDM risk. These findings support the important role of optimal dietary fatty acids composition in the prevention of GDM.