Birthweight in women with potential gestational diabetes mellitus - an effect of obesity rather than glucose intolerance?

Background. The purpose was to compare the influence of varying levels of glycemia on the perinatal outcome. Methods. The data charts of 383 women screened for gestational diabetes mellitus with an oral glucose tolerance test during two birth years were retrospectively evaluated. In 55 women gestational diabetes mellitus was diagnosed and treated with diet. The non-diabetic women (n=328) were subdivided into a borderline diabetes group (n=74) and a normal group (n=254) on the basis of the oral glucose tolerance test result. The birth registry of 8196 singleton pregnancies from The Perinatal Research Unit at Skejby University Hospital served as the background population. Results. Birthweight was highest in the borderline group. Weight increase during pregnancy was larger in the non-diabetic than the gestational diabetic women (15 vs. 8 kg p<0.01). The women with less increase of body weight delivered neonates with lower birthweight than those with higher increase. Birthweight was associated with maternal weight during pregnancy (p<0.01). Birthweight ratio increased with increasing glucose intolerance. Vaginal delivery rate was less and cesarean section rate higher in women with gestational diabetes mellitus compared to the non-diabetic women. No significant difference was found in the incidence of hypertensive disorders during pregnancy or neonatal morbidity. Conclusions. Even minor hyperglycemia is associated with increasing birthweight. Birthweight is reduced in GDM when dietary treatment is instituted and effect on weight gain is achieved.