Epidemiology of pregnancy-induced hypertension and preeclampsia in Type 1 (insulin-dependent) diabetic pregnancies in Sweden

Background. The object of this study was to examine if there is an association between pregnancy-induced hypertension (PIH) and/or preeclampsia (PE) and glycemic control assessed by HbA1c in early type 1 diabetic pregnancy, as well as factors such as maternal age, parity, duration of diabetes, presence of diabetes microangiopathy. Methods. The nationwide collaborative study included 491 type 1 diabetic pregnancies corresponding to about 80% of the diabetic pregnancies during the study period 1983-1985. A blood sample for determination of HbA1c was obtained in early gestation (median 9 (5-16) weeks). Results. The rate of PIH/PE was 20.6% in the type 1 diabetic pregnancies compared to 5.0% in the background population. The type 1 diabetic pregnancies complicated by PIH/PE were associated with significantly longer duration of diabetes, higher initial HbA1c (8.1% vs 7.4%, p<0.01), higher rate of nephropathy and retinopathy, while there were no significant differences in maternal age or parity compared to those without PIH/PE. Discriminant analysis revealed that occurrence of nephropathy (p<0.001), retinopathy (p<0.01) and high HbA1c (p<0.01) in early pregnancy were independently and significantly associated with occurrence of PIH/PE. Among the 463 patients without prepregnancy proteinuria 38 (8.2%) had PIH and 53 (11.5%) PE. The group with PE had, compared to the no PIH/PE group, significantly higher HbA1c (8.2% vs 7.4%, p<0.01). HbA1c was not significantly different between the PIH and the no PIH/PE group (7.5% vs 7.4%). Both the PIH and the PE group had significantly higher rate of retinopathy compared to the no PIH/PE group. If early HbA1c was equal to or above control mean by +8 s.d., i.e. greater than or equal to 10.1% the PI rate was 31.0% compared to 10.2% in those with HbA1c below that value. Conclusions. We conclude that poor glycemic control in early pregnancy is associated with increased risk of PE in non-proteinuric type 1 diabetic pregnancies.