In many locales type 2 (non–insulin-dependent) diabetes mellitus (DM) complicates pregnancy more often than type 1 diabetes, but less is known about perinatal mortality in the former condition. For this reason the investigators collected mortality data over the years 1985 to 1997 at a New Zealand diabetes clinic. A total of 434 pregnancies occurred in women with type 2 diabetes, 178 of whom were first diagnosed with gestational diabetes mellitus (GDM) and found to have type 2 diabetes in the early postpartum period. There were 160 other pregnancies in women with type 1 diabetes and 932 in women with GDM. Perinatal deaths were classified as intermediate (20–28 weeks’ gestation) or late fetal death or neonatal death up to 1 month after birth. Women were screened for GDM at 24 to 28 weeks’ gestation. Diabetes care included dietary counseling, home blood glucose monitoring, and insulin when necessary to maintain glycemic control (fasting blood sugar of 4–45.5 mmol/liter and a 90-minute postprandial value <7.5 mmol/liter).
Women with type 2 diabetes were significantly older than those with type 1 diabetes, had higher parity, were more obese, and were first seen significantly later in pregnancy. Fewer than 10 percent of those known to have type 2 diabetes were taking insulin at presentation, but all except 4 percent eventually did receive insulin, as did 87 percent of those first thought to have GDM. Women with type 2 diabetes had operative delivery less often than those with type 1 diabetes. Overall perinatal mortality was 12.5 per 1000 for the nondiabetic control population, the same for women with type 1 diabetes, 39.1 per 1000 in women with type 2 diabetes, and 16.2 per 100 for women with GDM. Perinatal mortality in women with newly presenting type 2 diabetes mellitus was 56.2 per 1000, compared with 8.9 per 1000 for the others with GDM. Intermediate fetal deaths and early neonatal deaths were about 2.5-fold more frequent in women with type 2 diabetes than in the control population, and late fetal deaths were increased 7-fold. Four other women had their pregnancies terminated before 24 weeks’ gestation. Congenital malformations explained two of five early neonatal deaths.
Perinatal mortality is significantly increased in women with type 2 diabetes mellitus, including those with GDM who have undiagnosed type 2 diabetes. Factors other than glycemic control, such as maternal obesity, may contribute to the relatively high rate of fetal loss in these women.
Diabetes Med 2000;17:33–39
Department of Medicine and Department of Obstetrics and Gynaecology, University of Auckland; and Diabetes Pregnancy Clinic, National Women’s Hospital, Auckland, New Zealand