Risk of post-pregnancy hypertension in women with a history of hypertensive disorders of pregnancy: nationwide cohort study

Abstract

Objectives To determine how soon after delivery the risk of post-pregnancy hypertension increases in women with hypertensive disorders of pregnancy and how the risk evolves over time.Design Nationwide register based cohort study.Setting Denmark.Populations 482 972 primiparous women with a first live birth or stillbirth between 1995 and 2012 (cumulative incidence analyses), and 1 025 118 women with at least one live birth or stillbirth between 1978 and 2012 (Cox regression analyses).Main outcome measures 10 year cumulative incidences of post-pregnancy hypertension requiring treatment with prescription drugs, and hazard ratios estimated using Cox regression.Results Of women with a hypertensive disorder of pregnancy in a first pregnancy in their 20s, 14% developed hypertension in the first decade post partum, compared with 4% of women with normotensive first pregnancies in their 20s. The corresponding percentages for women with a first pregnancy in their 40s were 32% and 11%, respectively. In the year after delivery, women with a hypertensive disorder of pregnancy had 12-fold to 25-fold higher rates of hypertension than did women with a normotensive pregnancy. Rates in women with a hypertensive disorder of pregnancy were threefold to 10-fold higher 1-10 years post partum and remained twice as high even 20 or more years later.Conclusions The risk of hypertension associated with hypertensive disorders of pregnancy is high immediately after an affected pregnancy and persists for more than 20 years. Up to one third of women with a hypertensive disorder of pregnancy may develop hypertension within a decade of an affected pregnancy, indicating that cardiovascular disease prevention in these women should include blood pressure monitoring initiated soon after pregnancy.

Fig 1 Ten year cumulative incidences of hypertension by years since first pregnancy in women with and without a hypertensive disorder of pregnancy, by age at first delivery, Denmark, 1995-2012. Follow-up began in 1995 or three months post partum, whichever came later

Fig 2 Hazard ratios for hypertension by severity of hypertensive disorder of pregnancy (if any) in the most recent pregnancy and time since most recent pregnancy, among women with at least one live birth or stillbirth in Denmark, 1978-2012. Hazard ratios compare rates of hypertension among women with severe pre-eclampsia (orange), moderate pre-eclampsia (green), and gestational hypertension (black) in the latest pregnancy with rates of hypertension in women whose most recent pregnancy was normotensive. Follow-up began in 1995 or three months post partum, whichever came later. Hazard ratios are adjusted for maternal age, maternal birth year, and parity (see also supplementary figure 1 for corresponding figure with hypertensive disorders of pregnancy classified by timing of delivery)

Fig 3 Hazard ratios for hypertension by history of most severe hypertensive disorder of pregnancy and attained maternal age, among women with at least one live birth or stillbirth in Denmark, 1978-2012. Hazard ratios compare rates of hypertension among women with severe pre-eclampsia (orange), moderate pre-eclampsia (green), and gestational hypertension (black) as their most severe hypertensive disorder of pregnancy (cumulative history over all pregnancies) with rates of hypertension in women whose pregnancies were all normotensive. Follow-up began in 1995 or three months postpartum, whichever came later. Hazard ratios are adjusted for maternal age, maternal birth year, parity, and time since most recent pregnancy

Fig 4 Hazard ratios for hypertension by hypertensive disorder of pregnancy sequence in two first pregnancies by number of years since the second pregnancy, among women with at least two live births or stillbirths in Denmark, 1978-2012. Hazard ratios compare rates of hypertension among women with a hypertensive disorder of pregnancy in first pregnancy but not in the second (green), a normotensive first pregnancy followed by a hypertensive disorder of pregnancy in second pregnancy (red), and hypertensive disorders of pregnancy in two successive pregnancies (purple), with rates in women with two successive normotensive pregnancies. Follow-up began in 1995 or 3 months after the second delivery, whichever came later. Hazard ratios are adjusted for maternal age, maternal birth year, and parity