Treatments for gestational diabetes and impaired glucose tolerance in pregnancy

Tuffnell, Derek J, West, Jane, Walkinshaw, Stephen A

Gestational diabetes and impaired glucose tolerance (IGT) in pregnancy affects between 3 and 6% of all pregnancies and both have been associated with pregnancy complications. A lack of conclusive evidence has led clinicians to equate the risk of adverse perinatal outcome with pre-existing diabetes. Consequently, women are often intensively managed with increased obstetric monitoring, dietary regulation, and in some cases insulin therapy. However, there has been no sound evidence base to support intensive treatment. The key issue for clinicians and consumers is whether treatment of gestational diabetes and IGT will improve perinatal outcome. The objective of this review was to compare alternative policies of care for women with gestational diabetes and IGT in pregnancy. We searched the Cochrane Pregnancy and Childbirth Group trials register (12 September 2002) and the bibliographies of relevant papers. The Cochrane Central Register of Controlled Trials was also searched (The Cochrane Library, Issue 3, 2002). Randomised controlled trials comparing alternative management strategies for women with gestational diabetes and IGT in pregnancy. Quality was assessed according to the criteria defined by the Cochrane Reviewers' Handbook. Data were extracted and checked independently by two reviewers. Any disagreements were resolved through discussion with the third reviewer. Three studies with a total of 223 women were included. All three included studies involved women with IGT. No trials reporting treatments for gestational diabetes met the criteria. There are insufficient data for any reliable conclusions about the effect of treatments for IGT on perinatal outcome. The difference in abdominal operative delivery rates is not statistically significant (relative risk (RR) 0.86, 95% confidence interval 0.51 to 1.45) and the effect on special care baby unit admission is also not significant (RR 0.49, 95% confidence interval (CI) 0.19 to 1.24). Reduction in birthweight greater than 90th centile (RR 0.55, 95% CI 0.19 to 1.61) was not found to be significant. This review suggests that an interventionist policy of treatment may be associated with a reduced risk of neonatal hypoglycaemia (RR 0.25, 95% CI 0.07 to 0.86). No other statistically significant differences were detected. A number of outcomes are only reported by one study resulting in a small sample and wide confidence intervals. There are insufficient data for any reliable conclusions about the effects of treatments for impaired glucose tolerance on perinatal outcome.