VALUE OF EARLY GLUCOSE-TOLERANCE TESTING IN WOMEN WHO HAD GESTATIONAL DIABETES IN THEIR PREVIOUS PREGNANCY

The patterns of glucose tolerance, clinical characteristics, and follow-up results of 1,027 pregnant women who had gestational diabetes diagnosed in their previous pregnancy, were analyzed. Glucose tolerance testing was performed before 24 weeks (mean 16.6 +/- 4.5 weeks) in 180 women (group 1); when the result was normal the test was repeated at 26-30 weeks' gestation. In this group the incidence of recurrent gestational diabetes was 49.4%, and early testing diagnosed 61.8% of cases. Group 2 consisted of 685 women in whom glucose tolerance was tested only at 26-30 weeks' gestation. In this group the incidence of recurrent gestational diabetes was 34.0%. Group 3 consisted of 162 women in whom glucose tolerance was not tested in the subsequent pregnancy. Perinatal mortality rates in Groups 1 to 3 were 2.2%, 0.6% and 3.1% respectively in the pregnancy subsequent to that in which gestational diabetes was first diagnosed. The risk of emerging diabetes mellitus on follow-up was greater in women in whom gestational diabetes was diagnosed early than in those diagnosed at the usual time (33.3% versus 12.5%, p<0.05). Analysis of the 13 perinatal deaths in Groups 1-3 revealed 5 that were potentially avoidable; none of the 3 women with recurrent gestational diabetes in the early tested group who had perinatal deaths received insulin in their subsequent pregnancies. Although perinatal deaths are unavoidable in some high-risk pregnancies associated with gestational diabetes, this study suggests that early diagnosis of gestational diabetes may allow further reduction of perinatal mortality. However, early diagnosis is wasted unless it results in early treatment, including insulin therapy when dietary measures fail to control hyperglycaemia. Women who have had gestational diabetes in a previous pregnancy warrant glucose tolerance testing early in a subsequent pregnancy, since those with recurrent disease, especially when the degree of intolerance is severe, have a high perinatal mortality rate, which may be improved by early management.