Pregravid body mass index as a predictor of gestational diabetes mellitus

It has been well documented that overweight or obesity before pregnancy is a strong predictor of gestational diabetes mellitus (GDM). The aim of this study was to assess the risk of GDM in women who were classified on the basis of pregravid body mass index (BMI) as normal weight and underweight.

We analysed medical records of 1121 women with GDM who were referred to the Outpatient Clinic for Diabetic Pregnant Women in Szczecin (north-west part of Poland) between January 2001 and December 2005. The control group consisted of 1011 healthy pregnant women. All the women were Caucasian, were aged > or = 18 years and had single pregnancies.

The cut point for BMI as a risk indicator for GDM was 22.85 kg/m(2) (odds ratio = 1.91; 95% confidence interval 1.5-2.1; sensitivity 47.8%, specificity 65.9%). In all of the analysed BMI ranges, except for the underweight group, significant relationships between pregravid BMI and GDM were found and BMI was the strongest predictor for GDM treated with insulin. Of all women with GDM, 25.7% were treated with insulin. The percentage of women requiring insulin therapy significantly increased with an increase of BMI across all studied categories.

Not only in overweight but also in normal-weight women, the risk for GDM increases with increases in pregravid BMI and adjustment for confounding variables (age, prior GDM and parity) did not influence this relationship. Pregravid BMI is a strong predictor for GDM requiring insulin treatment.