Hypertension during pregnancy is associated with increased risk of later cardiovascular disease, kidney disease and diabetes
- Department of Clinical Sciences, Clinica Ostetrica Ospedale Salesi, Università Politecnica Marche, Ancona, Italy
- Correspondence to: Professor Andrea L Tranquilli, Department of Clinical Sciences, Clinica Ostetrica Ospedale Salesi, Università Politecnica Marche, Ancona, Via Corridoni 11, Ancona 60123, Italy;
Commentary on: .
Implications for practice and research
Blood pressure (BP) should be measured and recorded at each clinic visit in pregnancy.
Hypertensive disorders of pregnancy should be carefully classified, distinguishing among ‘chronic’, occurred for the first time in pregnancy after 20 weeks, and presence or absence of proteinuria.
Follow-up and lifestyle changes should be prescribed for women who suffered from hypertensive disorders in pregnancy to reduce the risk of cardiovascular disease and death from myocardial infarction later in life.
Databases should be organised for pregnancy outcomes to provide a basis for future research, including the presence and the class of hypertensive diseases of pregnancy other than pure data such as mode and timing of delivery and neonatal weight, etc.
Hypertension in pregnancy is a complex set of conditions that affects as many as 10% of all pregnant women. It is generally classified as hypertension of new onset in pregnancy, with subclassifications of gestational hypertension or pre-eclampsia (hypertension and proteinuria >0.3 g/24 h urine) and pre-existing, chronic hypertension with or without superimposed pre-eclampsia.1
Until now, hypertension in pregnancy has been considered according to its effect on maternal and fetal health during pregnancy, and gestational conditions have been thought to extinguish with pregnancy and placental removal. Current epidemiological research highlights how those conditions have long-term effects on women's health2 especially in terms of morbidity and mortality from cardiovascular disease in the fifth and sixth decades.
The study originated from the Northern Finland Birth Cohort 1966 database which covered over 96% of births in the area for a total of 12 055 women. Pregnancy care was provided by midwives. BP values of >145 systolic and >95 diastolic were selected to define hypertension. Proteinuria was assessed by dipsticks; when positive was confirmed by further tests to confirm values >0.3 g/L in a 24-h urine collection. Eight classes were identified by combining the two parameters: (1) normotensive (BP<145/95); (2) isolated systolic; (3) isolated diastolic; (4) isolated hypertension with proteinuria; (5) gestational hypertension (BP>145/95 after 20 weeks’ gestation in previously normotensive women); (6) pre-eclampsia (gestational hypertension with proteinuria); (7) chronic hypertension (hypertension before 20 weeks or 6 weeks after delivery) and (8) superimposed pre-eclampsia/eclampsia (eclampsia/proteinuria occurring during pregnancy in chronic hypertensive women). Pregnancy data were compared with disease outcomes over the subsequent 40 years, as recorded in the Finnish Special Refund Entitlement Register (1967–2000), Hospital Discharge Register (1972–2008) and Population Register and Register of Causes of death (1962–2006).
Hypertensive women were generally older, heavier and more frequently nulliparous. Women who suffered from hypertension in pregnancy showed an increased risk for cardiovascular and ischaemic heart disease; heart failure; ischaemic cerebrovascular disease; chronic renal disease; arterial hypertension and diabetes mellitus. The risk of death from myocardial infarction (MI) in the sixth decade of age is the most common and present in almost all the classes. The risk is not equally distributed. Women with superimposed pre-eclampsia/eclampsia are at highest risk for cardiovascular events, with a hazard risk (HR) versus normotensive pregnant women of 5.12 for death from MI (mean age at first event 58 years); HR 3.18 for MI (mean age at first event 65 years); HR 3.32 for heart failure (mean age at first event 65 years).
This paper strongly supports the upcoming evidence that hypertensive disorders of pregnancy are not solely confined to pregnancy and do not vanish with delivery. Furthermore, even ‘minor’ classes identified as isolated hypertension, bear risk for future health.
Of course, there are different forms of hypertension in this context. ‘Pure gestational’ hypertension and pre-eclampsia, of placental origin, may cause vascular stress that can predispose or induce vascular diseases later in life. ‘Chronic’ forms may be aggravated in pregnancy and result in the worst long-term outcomes. Pregnancy may also uncover individual susceptibility to subsequent chronic diseases.
There are two critical points in this study. The definition of hypertension with values >145/95 is different from all currently used which identify the cut-off at >140/90.1 This does not change the importance of the findings and conclusions, rather, it confirms and possibly underestimates the importance of hypertension in pregnancy on long-term outcomes. A second criticism should be made on the classes the authors ‘discover’ in their study. What they call ‘isolated hypertension’ is in the current classification as ‘gestational hypertension’.1 The authors, in fact, define hypertension as the occurrence of elevated systolic and diastolic, while the most common classifications consider systolic and/or diastolic.1 Therefore, the findings for those classes with isolated hypertension should be better reclassified as gestational hypertension and pre-eclampsia.
Whatever the minor deviations from the more common classifications are, the strength of the whole study is in the powerful database created in 1960 in Finland which should serve as a model for planning future research.