A cohort study of epidemiological associations and outcomes of pregnancies with hypertensive disorders

Objective: To determine the associations of maternal biological and sociodemographic characteristics with different types of hypertensive disorders of pregnancy, their incidence, and the outcomes of the pregnancies. Method: A prospectively collected birth cohort of 9247 singleton pregnancies from the northernmost provinces of Finland with the expected date of delivery falling between July 1, 1985 and June 30, 1986. Results: The total number of women with elevated blood pressure was 1793 (17.2%). The incidence of chronic hypertension was 4.3%, that of gestational hypertension 11.0%, and that of preeclampsia 1.9%. Advanced maternal age and high prepregnancy body weight were associated with an increased risk of chronic hypertension in parous women and of gestational hypertension and preeclampsia in nulliparous women. A risk of preeclampsia also arose from low education and employment during pregnancy. The occurrence of all hypertensive complications was lower among smokers than nonsmokers. Previous abortions had a slight, but nonsignificant, protective effect, and the method of contraception had no influence on the prevalence of preeclampsia among the primiparous women. A seasonal trend in the prevalence of preeclampsia was observed, with a peak in April. The highest perinatal mortality was associated with chronic hypertension (2.8% CI 1.6-5.0), regardless of superimposed preeclampsia, whereas gestational hypertension increased maternal and perinatal morbidity but not mortality. Preeclampsia was related to the highest rates of maternal complications and perinatal morbidity especially prematurity, SGA, and need of neonatal intensive care (28%). Conclusions: Certain maternal characteristics, such as advanced maternal age, nulliparity, obesity, low education, employment and chronic hypertension, are associated with hypertensive disorders during pregnancy and are known at the first visit to health care, Attention to the risk factors can enable supervision of the pregnancy with the aim of early detection of hypertension and its complications.