Fat mass accumulation during pregnancy in women with gestational diabetes mellitus

Objective: The objective of this study was to assess fat and fat-free mass deposition during gestation in normal women and in women with gestational diabetes mellitus. Methods: Twenty-two pregnant women were followed prospectively from 19 gestational weeks until term. Eight of these women were diagnosed with gestational diabetes mellitus during late gestation. At the initial visit, pregestational weight, height and medical history were obtained. At all visits, maternal weight was measured on a balance beam scale and body composition was determined using a bioimpedance meter. Reactance and resistance values were used to calculate total body water, lean body mass and body fat. The women were followed until delivery, with a mean of five visits per patient. Results: No significant difference was found in either pregestational weight (71.8 ± 12.7 kg for controls versus 71.1 ± 10.0 kg for women with gestational diabetes mellitus) or body mass index (26.5 ± 5.2 kg/m² for controls and 29.3 ± 2.0 kg/m² for gestational diabetes women). By 20 weeks' gestation, the women with gestational diabetes were heavier than controls (84.7 ± 14.4 kg versus 74.5 ± 16.4 kg, respectively) but no significant difference was found in percentage body fat (37.5 ± 7.7% for controls and 40.1 ± 5.2% for gestational diabetes women) between the two groups. During the third trimester of pregnancy, the diabetic women increased their percentage fat mass at a greater rate than normal women (0.56 ± 0.23 versus 0.35 ± 0.13% per week; p < 0.017) while their weight gain during this period was similar (7.1 ± 4.4 versus 7.3 ± 2.8 kg; NS). Conclusion: Maternal fat mass accumulation during the third trimester of pregnancy in women with gestational diabetes exceeded that found in normal healthy controls. This accumulation could be related to the underlying condition (i.e. gestational diabetes) or alternatively, could be associated with the development of gestational diabetes by augmenting the physiological insulin resistance of pregnancy.