Diabetes in pregnancy.

Diabetes in pregnancy is predominantly either pre-existing type 1 or type 2 diabetes mellitus, or gestational diabetes, the latter defined as diabetes or glucose intolerance first diagnosed during the pregnancy. Gestational diabetes usually arises in the late second trimester and is common, affecting from 2–6% to 15–20% of pregnant women depending on diagnostic criteria and country of origin. Gestational diabetes is most commonly diagnosed on the basis of an oral glucose tolerance test performed at 24–28 weeks’ gestation by a plasma glucose at 0 minutes of more than 5.1 (or >5.6, depending on the authority) mmol/L, or at 120 minutes of more than 8.5 (or >7.8) mmol/L. The effect of pregnancy on maternal glycaemic control ceases very quickly post-partum, hence women with pre-existing diabetes taking insulin should immediately revert to their pre-pregnancy regimen after birth, but with a lower insulin dose.