Risk of development of diabetes mellitus in Chinese women with persistently impaired glucose tolerance after gestational diabetes.

OBJECTIVES To estimate the cumulative incidence for the development of diabetes mellitus in Chinese women with persistently impaired glucose tolerance after gestational diabetes, and evaluate putative risk factors. DESIGN Historical cohort study. SETTING A regional hospital in Hong Kong. PATIENTS Women with postpartum impaired glucose tolerance (as confirmed by a 75-gram oral glucose tolerance test 6 weeks after delivery) seen between January 2000 and December 2006. RESULTS After a mean follow-up period of 52 (standard deviation, 22; range, 12-106) months, 47 (20%) of the 238 women converted to diabetes mellitus. Concomitant postpartum impaired fasting plasma glucose levels increased the risk of future diabetes mellitus by 3.5-fold (95% confidence interval, 1.7-7.0; P=0.001) when compared to those with postpartum impaired glucose tolerance only. Based on multivariate analysis, only antepartum and postpartum fasting plasma glucose levels predicted future development of diabetes mellitus. At 1 year after delivery in 95/159 (60%) of the women, glucose tolerance regressed to normal, while in only 9/159 (6%) it progressed to diabetes mellitus. At this stage, 29% of those with impaired glucose regulation (impaired glucose tolerance, impaired fasting glucose or both) compared to 2% of those whose glucose tolerance reverted to normal developed diabetes mellitus upon subsequent follow-up (P<0.001). In all, 24/159 (15%) fulfilled the definition of metabolic syndrome and its presence was associated with 4.7-fold increased risk of future diabetes mellitus (95% confidence interval, 1.7-13.4; P=0.004). CONCLUSIONS Women with persistent postpartum impaired glucose tolerance after gestational diabetes have a high risk of developing diabetes mellitus. However, a significant proportion of these women regress to normal glucose tolerance 1 year after delivery, and their risk of progression to diabetes mellitus is lower than those with persistent impaired glucose regulation. Therefore, women with a history of gestational diabetes, particularly those with persistent glucose intolerance 6 weeks and 1 year after delivery, should have regular surveillance for the development of diabetes mellitus.