Modifiable determinants for gestational diabetes mellitus (GDM) include high pregnancy body mass index (BMI), inadequate or excessive gestational weight gain, diet during pregnancy, cigarette smoking and physical inactivity during pregnancy. To date, few studies examined the independent associations of each of these modifiable determinants with GDM risk. For these reasons, no recommendations on diet, weight or weight gain during pregnancy could be established in efforts to reduce the risk for GDM. The overarching aim of this doctoral dissertation research was to investigate if GDM risk is associated with modifiable determinants, in particular, prepregnancy weight status and dietary patterns during pregnancy in U.S. representative pregnant women. Four hypotheses of this research are: 1) prepregnancy weight status, independent from gestational weight gain, is a determinant for GDM; 2) prepregnancy weight status is associated with dietary patterns during pregnancy; 3) dietary patterns during pregnancy are associated with gestational weight gain; and 4) dietary patterns during pregnancy are associated with increased GDM risk in conjunction with an inflammatory marker.For hypothesis 1, we used the data of 219,868 pregnant women from 2004 to 2011 Pregnancy Risk Assessment Monitoring System (PRAMS). Multivariable logistic regression analyses were performed to examine the effect of prepregnancy BMI on GDM risk after controlling for the adequacy of gestational weight gain. For hypothesis 2, we analyzed the data of 795 U.S. pregnant women in the National Health and Nutrition Examination Survey (NHANES) 2003-2012. Multivariable logistic regression analyses were used to estimate the adjusted odds ratio (AOR) and 95% CIs for the association of prepregnancy weight status with dietary patterns during pregnancy assessed by the Healthy Eating Index (HEI)-2010 after controlling for confounders. For hypothesis 3, a total of 391 pregnant women in the NHANES 2003-2006 were included. Multivariable logistic regression analyses were performed to investigate the association between dietary patterns during pregnancy derived by factor analysis and the adequacy of gestational weight gain. For hypothesis 4, a total of 253 pregnant women were included in the NHANES 2003-2012. Multivariable logistic regression models were used to examine the relationship between dietary patterns using reduced rank regression and the risk of GDM.Women who were overweight or obese based on prepregnancy BMI compared to normal prepregnancy BMI had higher odds for GDM (AOR=1.79; 95% CI=1.68-1.92, AOR=2.78; 95% CI=2.60-2.96, respectively). Regardless of the adequacy of gestational weight gain, women who were overweight or obese before pregnancy had higher odds for GDM (hypothesis 1). Women who were obese before pregnancy had increased odds for being in the lowest tertile of HEI-2010 compared to those with normal prepregnancy BMI (AOR 5.50; 95% CI 2.05-14.77) after controlling for maternal sociodemographic variables, and physical activity (hypothesis 2). Women in the middle tertile of a ‘mixed’ dietary pattern had significantly lower odds of excessive gestational weight gain compared to those in the lowest tertile (AOR 0.39; 95% CI 0.15-0.99) (hypothesis 3). Multivariable AOR (95% CIs) for GDM comparing the highest with lowest tertiles of ‘added sugar, low fruits and vegetables’ dietary pattern was 12.61 (4.08-38.97), after controlling for maternal sociodemographic variables, prepregnancy BMI, gestational weight gain, energy intake, and log-transformed CRP (hypothesis 4). In conclusion, GDM risks are associated independently with prepregnancy weight status, gestational weight gain and a specific dietary pattern during pregnancy in U.S. representative pregnant women. These findings may provide scientific bases to establish recommendations on diet, weight or weight gain during pregnancy in efforts to reduce the risk for GDM.
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