The importance of diabetes in pregnancy arises through two unrelated phenomena: an increased predisposition to impaired glucose tolerance in late pregnancy and an adverse impact of the increased glucose on important obstetric outcomes. There are marked differences in clinical outcomes and management between pregnancies in which a clinically significant impairment of glucose tolerance was first noticed during pregnancy (‘gestational diabetes mellitus’) and those where type 1 or type 2 diabetes mellitus had been known prior to pregnancy (‘prepregnancy diabetes’). Historically, GDM has been defined as the diagnosis of clinically significant impaired glucose tolerance in pregnancy in a woman not previously known to be diabetic. This has recently been complicated by recognizing that some diabetes mellitus will present for the first time in pregnancy and lack of clarity as to where the lower threshold for diagnosis should best be placed. Type 1 diabetes is present in approximately 0.2% of pregnant women, and the numbers are largely stable. In contrast, type 2 diabetes was once uncommon in pregnancy but is now also as high as 0.2%. This is likely to continue to increase as increased numbers of overweight and obese women enter the reproductive years. Prepregnancy diabetes provides the model of how pregnancy and maternal disease impact on each other, and how good preconception, antenatal and intrapartum care can make an enormous difference for these women and their babies.
Cortisol metabolism in obese women with normal and impaired glucose tolerance
