Objective: To determine the influence of microalbuminuria on pregnancy outcome in women with type 1 diabetes.
Research design and methods: This prospective cohort study took place at the Obstetric Clinic at National University Hospital, Copenhagen, from January 1996 to February 2000. All Caucasian women with type 1 diabetes, unselected from the eastern part of Denmark, with a living fetus before 17 weeks of gestation on admission were asked to participate. For women with more than one delivery in the study period, only the first pregnancy was included. Of the remaining 246 women, 240 (98%) entered the study. They were categorized according to their urinary albumin excretion (normal urinary albumin excretion, <30 mg/24 h; microalbuminuria, 30-300 mg/24 h; or diabetic nephropathy, >300 mg/24 h) before pregnancy or in the first trimester.
Results: A total of 203 women (85%) had normal urinary albumin excretion, 26 (11%) had microalbuminuria, and 11 (5%) had diabetic nephropathy. Mean HbA(1c) at 2-6 weeks was 7.5% (SD 1.1), 8.1 (0.9), and 8.8 (1.3) (P < 0.001), respectively. Of all deliveries in women with normal urinary albumin excretion, microalbuminuria, and diabetic nephropathy, 35, 62, and 91% (P < 0.001), respectively, were preterm, and 2, 4, and 45% (P < 0.001), respectively, were small-for-gestational-age infants. Preeclampsia developed in 6, 42, and 64% of the women (P < 0.001), respectively. Category of urinary albumin excretion (P < 0.01) and HbA(1c) at 2-6 weeks (P < 0.05) were independently associated with preterm delivery.
Conclusions: The prevalence of preterm delivery is considerably increased in women with microalbuminuria, mainly caused by preeclampsia. Classification according to urinary albumin excretion and metabolic control around the time of conception are superior to the White classification in predicting preterm delivery in women with type 1 diabetes.