Hypertensive disorders during pregnancy predisposes to future hypertension and the risk persists for more than 20 years.

Women face substantially high risk of post pregnancy hypertension in the first year after the index pregnancy and the risk persists for more than 20 years, with 14- 32% for the first decade reports the result of a nationwide register based cohort study published in July issue of BMJ.

Nearly one third of women with hypertensive disorder of pregnancy will develop hypertension within 10 years of the affected pregnancy, so blood pressure monitoring should be initiated immediately after delivery.  

What is already known:

Women who have a history of hypertensive disorders while pregnant have 2 to 4-fold increased risk of developing essential hypertension, and a subsequent CV event.

But the data about the timing of developing hypertension and the time at which the screening of these at-risk women should begin is not known.

What the study adds:

This study gives us the chronology of events: How soon the women may develop hypertension, how long the risk will persist after the affected pregnancy and when to start monitoring these women for development of hypertension.

The study identified 482972 women through Danish civil registration system, of these 23235 (4.8%) women developed hypertensive disorder of pregnancy and 16611 developed hypertension during follow-up.

In a cohort of more than one million women delivering in Denmark from 1978-2012, the investigators formed two cohorts and followed them for estimation of cumulative incidence of post-pregnancy hypertension and the other cohort for the estimation of hazard ratios for post-pregnancy hypertension.

Women with chronic hypertension were excluded from the study.

In women who had normotensive first pregnancy in 20s, 30s, or 40s, the cumulative incidences of hypertension in the first 10 years after delivery were 4.0%, 5.7%, and 11.3%, respectively, whereas in women with hypertensive disorder the corresponding incidence were 13.7%, 20.3%, and 32.4%, respectively.

In women with history of hypertensive disorder in most recent pregnancy, the rates of developing hypertension were 12-fold to 25-fold higher in the first-year after delivery and up to 10-fold higher in the coming 10 years.

Women face 2 fold increase risk of developing hypertension, that lasts for the next 20 years, if they have a previous history of hypertensive disorder in pregnancy as compared to women who had normal blood pressure while pregnant.

Why this study is important:

Large cohort, elimination of selection and recall bias.

Data adjusted for age, parity, smoking status, diabetes and BMI.

Immediate post-partum period is very important: The risk of developing hypertension is highest shortly after an affected pregnancy but persists for more than 20 years.

The higher risk of hypertension in a decade after the affected pregnancy also indicates that the etiopathological process causing hypertension in later life, are already at play during the affected pregnancy.

A hypertensive disorder of pregnancy in the second pregnancy was more strongly associated with later hypertension than a hypertensive disorder of pregnancy in the first pregnancy.

Initiation of regular blood pressure assessments should begin soon after a pregnancy complicated by a hypertensive disorder of pregnancy for prompt identification of hypertension in these women.

What is needed in the future:

An algorithm to identify those at greatest risk (the subgroup most likely to benefit from screening) is urgently needed; identification of biomarkers that predict which women will develop hypertension after an affected pregnancy would be very useful.

Quantification of cardiovascular events that can be prevented by early identification of these at-risk women is also needed.

More randomized control trials to form policies on clinical follow up of such women.