The importance of postpartum glucose tolerance testing after pregnancies complicated by gestational diabetes

To review postpartum glucose tolerance in women with gestational diabetes and evaluate the role of formal 75 g oral glucose tolerance testing vs. fasting plasma glucose in screening for persistent abnormalities.

Retrospective study of 985 pregnancies over a 10 year period in a mixed ethnic cohort of women who underwent follow-up glucose tolerance testing at 6 weeks postpartum. Diagnosis obtained by oral glucose tolerance test was tested against that from the fasting plasma glucose value.

There were 272 abnormal postpartum oral glucose tolerance test results (27.6%), with 109 women identified as having frank diabetes. Eleven of these (10%) had fasting plasma glucose < or =6.0 mmol/l, as did 62 of 114 cases of impaired glucose tolerance. A fasting plasma glucose concentration of > or =6.1 mmol/l correctly identified abnormal glucose tolerance in 199 of 272 cases (sensitivity 0.73). South Asian women were much more likely to have persistent abnormalities of glucose tolerance than were Europeans (32 vs. 15%, chi(2)P < 0.0001).

A postpartum fasting plasma glucose measurement alone is not sensitive enough in our population to classify glucose tolerance status accurately. A formal postpartum oral glucose tolerance test is therefore needed to facilitate early detection and treatment.