Prepregnancy obesity and the risk of gestational diabetes mellitus

Background: Prepregnancy obesity is associated with increased risk for adverse pregnancy outcome such as gestational diabetes mellitus (GDM), gestational hypertension, preeclampsia, fetal macrosomia and the need for cesarean delivery. The objectives of this study assessed whether Thai women classified as obese according to WHO's recommended body mass index (BMI) for Asians were at risk for developing gestational diabetes mellitus (GDM) and other complications such as preeclampsia, gestational hypertension and fetal macrosomia. Methods: Two hundred and forty women participated in this study and followed prospectively until delivery. Half of the women (n = 120) were obese (BMI >= 27.5 kg/m(2)) and the other half (n = 120) had normal weight (BMI > 18.5-23 kg/m(2)). Maternal demographic data, obstetric and neonatal outcomes from both groups were compared to each other. Relative risk and 95% confidence interval (CI) were calculated. Results: Compared to normal weight women, obese Thai women were not at increased risk for gestational diabetes mellitus (RR = 0.9 [95% CI 0.6-1.4]). Relative risk of preeclampsia and fetal macrosomia in obese women were 0.7 [95% CI 0.2-3.3] and 1.4 [95% CI 0.5-4.3], respectively. Relative risk of gestational hypertension in obese women was 12 [95% CI 1.6-90.8]. Conclusion: When WHO's classification of obesity was used for Asian populations, prepregnancy obesity without metabolic problems did not increase the risk for GDM, preeclampsia and fetal macrosomia in Thai women. But, prepregnancy obesity continued to increase the risk for developing gestational hypertension.