Relationship between haemoglobin A1C in early type 1 (insulin-dependent) diabetic pregnancy and the occurrence of spontaneous abortion and fetal malformation in Sweden.

This prospective nationwide study examined the relationship between diabetic control in early pregnancy as assessed by HbA1C and the incidence of spontaneous abortion and fetal malformation. HbA1C and plasma C-peptide were determined in 532 women with Type 1 (insulin-dependent) diabetes mellitus, corresponding to approximately 80% of all the diabetic pregnancies in the country during the study period 1982-1985, and 222 non-diabetic control women. Median gestational week for sampling was 9.0 in the Type 1 diabetic and 10.0 in the control group. The median value of HbA1C was 7.7% in the diabetic and 5.3% in the control group (p less than 0.001). The rates of spontaneous abortion, 7.7% vs 7.2%, and malformation, 4.3% (major 2.0%) and 2.4% (major 1.0%), were not significantly different between the diabetic and control group, respectively. These rates of malformation were not significantly different from the national figures of 4.55% (major 1.75%). Much elevated HbA1C, i.e., greater than 10.1% equal to 8 SD above the normal mean control value, was significantly associated with the occurrence of spontaneous abortion (p less than 0.001) and malformation (p less than 0.01). Discriminant analysis revealed that after correction had been made for the significant value of HbA1C to predict the occurrence of spontaneous abortion and malformation, no further predictive power was displayed by measurable plasma C-peptide, maternal age or duration of diabetes or presence of diabetic microangiopathy. We conclude that poor metabolic control in early pregnancy contributes to an increased risk of both spontaneous abortion and fetal malformation.