The Bernese gestational diabetes (GDM) project: Does pre-pregnancy BMI and weight gain in the first half of the pregnancy influence the development of GDM?

The prevalence of gestational diabetes mellitus (GDM) is increasing worldwide and pre-existing metabolic disorders such as prediabetes or overweight/obesity are predisposing factors. The aim of the following study was to investigate if weight gain and pre-pregnancy BMI contributes negatively in groups stratified by first trimester glycosylate haemoglobin (HbA1c).

Prospectively recruited pregnant women with an HbA1c test at ≤14 weeks of gestation were included. Two groups were defined according to HbA1c: group 1 HbA1c value < 5.7%, and group 2 with HbA1c between 5.7 – 6.4%. In both groups pre-pregnancy body weight, BMI as well as weight gain until GDM screening were compared. Statistical significance was considered p-value < 0.05.

During the study period 668 women met inclusion criteria. Of those 636 were included in group 1, and 32 (4.7%) in group 2. The prevalence of GDM in our population was 14.6%. Group 2 had a higher pre-pregnancy BMI (group 2: 26.8 ± 6.4 kg/m² vs. group 1: 23.3 ± 4.3 kg/m²; p = 0.02). Women who later developed GDM had a significant higher BMI in group 1 (GDM 25.57 ± 4.9 kg/m² vs.22.9 ± 4.0 kg/m², p = 0.0004) whereas BMI did not differ in group 2 (group 2: GDM 29.20 ± 7.9 kg/m² vs.25 ± 4.7 kg/m², p = 0.34). The weight gain until GDM screening between those with and without GDM did not differ (306 ± 168 g/week vs. 340 ± 156 g/week; p = 0.31).

In women with prediabetes the pre-pregnancy BMI is not different between those with and without GDM. On the contrary, in group 1 increased pre-pregnancy BMI seems to distinguish between women who develop GDM later on. Interestingly, weight gain before GDM diagnosis seems not to play an important role in GDM prevalence.