Older Underweight Pregnant Women Beat Young Overweight/Obese Ones on Incidence of Gestational Diabetes

OBJECTIVE: This study aimed to compare the incidence of gestational diabetes mellitus (GDM) in older underweight pregnant women vs young overweight/obese ones. METHODS: A multiracial retrospective-cohort study was conducted in five hospitals of Shanghai on 7,485 women who had been pregnant during 2018–2020. Incidence of GDM was equal to the proportion of GDM cases in the total number of cases observed in the same period. Comparison of GDM incidence of older underweight pregnant women and young overweight/obese ones was done with χ(2) tests. ORs and 95% CIs for GDM were estimated using univariate and multivariate logistic regression across gestation age and prepregnancy BMI. RESULTS: Advanced age (OR 1.09, 95% CI 1.072–1.11; P=0) and higher BMI (OR 1.57, 95% CI 1.112–2.212; P=0.01) were found to be risk factors of GDM. The incidence of 13.33% of older underweight pregnant women (age ≥35years, BMI <18.5 kg/m(2)) developing GDM was lower than that of young overweight/obese ones (age ≤24 years, BMI ≥24 kg/m(2)). For those aged ≥35years, it is advised that BMI be kept to <18.5 kg/m(2). For those aged ≤24 years, BMI control should not exceed 24 kg/m(2). CONCLUSION: Older underweight (age≥35years, BMI <18.5 kg/m(2)) pregnant women beat young overweight/obese ones (age ≤24 years, BMI ≥24 kg/m(2)) on incidence of GDM. Factors influencing obesity/overweight in GDM were high maternal age, though being young is a promising protective factor for GDM and tolerance of BMI is promoted, but should be limited to certain ranges. Being older increased the chances of developing GDM, but those with lower BMI still had lower GDM incidence than younger pregnant women.