This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.
High blood pressure increases the risk of diseases of the heart and blood vessels (cardiovascular disease). New research suggests that, for women with high blood pressure, having a pregnancy complication (such as early birth) further increases their risk of cardiovascular disease in future.
Researchers analysed health records of more than 1.2 million women who had given birth. They found that high blood pressure at any stage of life was linked with an increased risk of 12 cardiovascular diseases (including stroke and heart attack), as expected. The risk was even higher for women who also had complications during pregnancy. This was true even after controlling for ethnicity, number of pregnancies, and family history of cardiovascular disease.
Clinicians could use these findings to counsel women about their cardiovascular risk before, during, and after pregnancy. They could advise women at higher risk to make lifestyle changes (such as diet and exercise) to improve their health. The researchers say women who have high blood pressure and / or complications during pregnancy could benefit from early screening for cardiovascular disease.
What’s the issue?
Pregnant women with high blood pressure have an increased risk of complications during pregnancy, such as giving birth early or having a baby with an unexpectedly low birthweight.
These women are also at risk of cardiovascular disease because of their high blood pressure.
Before this study, it was unclear whether pregnancy complications add to the risk of cardiovascular disease in women with high blood pressure. This study investigated that question.
The researchers analysed the health records of more than 1,250,000 women in England who gave birth between 1997 and 2016. 12,698 (0.7%) had high blood pressure, 2,554 (20%) of whom had pregnancy complications (including early birth, low birth weight, and stillbirth). During follow-up (9 years on average), 16,499 women had a cardiovascular event or disease (such as stroke, heart attack, heart failure).
Compared to women with normal blood pressure and no complications during pregnancy:
- women with high blood pressure had twice the risk of cardiovascular disease
- women with both high blood pressure and complications during pregnancy had 3 times the risk of cardiovascular disease.
The raised risk of cardiovascular disease among women with high blood pressure remained after adjusting results for ethnicity, number of pregnancies, and family history of cardiovascular disease. Most women (66%) who had cardiovascular disease were younger than 40.
Why is this important?
High blood pressure is linked with a higher risk of cardiovascular disease, especially in women who had pregnancy complications. Clinicians could discuss these findings with women before, during, and after pregnancy.
Clinicians closely monitor and manage pregnant women’s blood pressure. These findings suggest that the practice may not only reduce pregnancy complications, but also, women’s risk of cardiovascular disease. Clinicians could encourage women with high blood pressure to take medicines as prescribed and to make lifestyle changes, such as exercising and having a healthy diet.
This study shows that pregnancy complications are linked with cardiovascular disease, but not that they cause it. The interaction between pregnancy complications and cardiovascular events is not fully understood.
Adults aged 40 – 74 who are not known to be at high risk of cardiovascular disease, are offered a routine NHS Health Check every 5 years. In England and Wales, the QRISK3 risk assessment is used to calculate their risk of cardiovascular disease, based on blood pressure, obesity, smoking, blood cholesterol and other factors. But QRISK3 does not consider female-specific risk factors, including pregnancy complications. The researchers suggest that adding questions about pregnancy complications would help identify those at increased risk of cardiovascular disease.
Some professional societies, such as the American Heart Association and American College of Obstetricians and Gynaecologists, include recommendations for long-term management of women who had pregnancy complications. They suggest that these women should be referred for cardiovascular disease screening in the year following an affected pregnancy.
The National Institute for Health and Care Excellence guidelines recommend that women with high blood pressure during pregnancy be given advice on lifestyle modifications, such as avoiding smoking and maintaining a healthy weight. But NICE does not recommend early cardiovascular follow up for these women.
The researchers recommend increased monitoring of heart and blood pressure, with earlier screening considered, for women with high blood pressure and pregnancy complications. They say this could reduce the burden of cardiovascular disease in this high risk group.
The researchers are carrying out a similar study using data from Sweden. This will confirm if the findings are also true outside of England.
You may be interested to read
This is a summary of: Al Khalaf S, and others. Association Between Chronic Hypertension and the Risk of 12 Cardiovascular Diseases Among Parous Women: The Role of Adverse Pregnancy Outcomes. Hypertension 2023; 80: 1427 – 1438.
Information on high blood pressure during pregnancy from Blood Pressure UK.
Information on keeping healthy during pregnancy from Tommy's.
Information on taking part in NIHR studies regarding high blood pressure.
Funding: This study was supported by an NIHR Research Professorship.
Conflicts of Interest: None declared.
Disclaimer: NIHR Alerts are not a substitute for professional medical advice. They provide information about research which is funded or supported by the NIHR. Please note that views expressed in NIHR Alerts are those of the author(s) and reviewer(s) at the time of publication. They do not necessarily reflect the views of the NHS, the NIHR or the Department of Health and Social Care.