Hypertensive disorders of pregnancy in women with Type 1 and Type 2 diabetes

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Abstract
Aims Hypertensive disorders in pregnancy are common in women with Type 1 diabetes and can be associated with adverse fetal outcomes, but little is known about hypertension in pregnancy in women with Type 2 diabetes. The aim of this study was to compare the incidence and outcomes of, and risk factors for, hypertension in pregnancy in women with Type 1 and Type 2 diabetes. Methods One hundred consecutive singleton pregnancies in women with Type 2 and 100 in women with Type 1 diabetes were studied. Hypertension in pregnancy was classified according to Australasian Society for the Study of Hypertension in Pregnancy guidelines. Outcomes of pregnancy examined included birth weight, rates of caesarean section, premature delivery and special care unit admission, and perinatal mortality. Results The overall incidence of hypertension in pregnancy was similar in Type 2 and Type 1 diabetes (41% vs. 45%), but the distribution of subtypes differed (P = 0.028). Women with Type 2 diabetes had more chronic hypertension (diagnosed at < 20 weeks gestation), but less preeclampsia than women with Type 1 diabetes. Hypertension in pregnancy was strongly associated with a number of adverse outcomes, but the impact of hypertension was significantly less for Type 2 diabetes than it was for Type 1 (premature delivery, P < 0.005; admission to Special Care Unit, P < 0.01; caesarean section, P = 0.05). This was, in part, because the frequency of adverse outcomes was greater in women with preeclampsia. Nulliparity, poor glycaemic control at presentation, and early pregnancy blood pressure and not smoking were risk factors for hypertension of similar magnitude in both types of diabetes. Significant effects of duration of diabetes and obesity were not seen in Type 2 subjects, but were in Type 1 (P < 0.01, P < 0.05, respectively). Early pregnancy albumin excretion rate was increased more frequently in Type 2 subjects than in Type 1 (P < 0.035), but was less strongly associated with the development of preeclampsia (P < 0.035). Conclusions The incidence of hypertension in pregnancy is similar in Type 2 and Type 1 diabetes, but the different population characteristics are reflected in a significantly different pattern of types of hypertension. Hypertension has less impact on adverse outcomes in Type 2 diabetes. Some risk factors for hypertension also differ between Type 2 and Type 1 diabetes.