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Women who become pregnant after fertility treatment are at increased risk of cardiovascular disease (conditions affecting the heart and blood vessels) and complications during birth. Research outlined the risks associated with these pregnancies. It concluded, however, that the overall risks are low.  

Women having fertility treatment often have risk factors (such as being older) that are associated with complications during birth. They are also more likely to have obesity, high blood pressure and other risk factors for cardiovascular disease than women who became pregnant naturally (unassisted).

However, little is known about the additional risk of becoming pregnant after fertility treatment (assisted conception). This large study was based on medical records in the US. It compared assisted to unassisted conception.

Pregnant women who had had fertility treatment were more likely to have acute kidney injury (kidneys stop working correctly) and to develop an abnormal heart rhythm (arrythmia). In addition, these pregnancies had more birth complications. Babies were more likely to be delivered by surgery (caesarean delivery) or to be born early (premature).  

The research suggests that women need to know about the associated risks before starting fertility treatment. Clinicians may need to monitor their health more carefully throughout pregnancy and especially during delivery.

More information on fertility treatments and cardiovascular disease is available on the NHS website.

What’s the issue?

Couples with fertility problems may not be able to become pregnant without fertility treatment. For women, this could mean taking drugs to control the release of an egg, surgery to remove scarring or blockage, or having a fertilised egg implanted in the womb (in vitro fertilisation or IVF).

All pregnancies increase women’s risk of cardiovascular disease. Pregnant women who have fertility treatment are more likely to be older, have diabetes, or high blood pressure than women who conceive naturally. These factors increase their risk of cardiovascular disease and complications during birth.

This US study explored whether the assisted conception itself further raised their risk of cardiovascular disease and complications during birth (compared with unassisted pregnancies).

What’s new?

The study was based on a large US database covering the outcomes of pregnancies. It compared 106,000 pregnancies through assisted conception with 34 million through natural conception between 2008 and 2016.

Overall, women who had assisted conception were older (35 years on average) than those with natural conception (28 years). They were wealthier, more likely to be White, and to have multiple long-term conditions such as obesity, diabetes, high blood pressure and high cholesterol (high levels of fat in the blood).

Between 2008 and 2016, the number of pregnancies through assisted conception increased. These pregnancies also became more common in women with multiple long-term conditions.

The researchers accounted for age, race, multiple long-term conditions, and the average income of the local area. These factors could influence someone’s chance of having cardiovascular disease or complications during birth.

Compared with women who conceived naturally, those who had fertility treatment to become pregnant were:

  • 2.5 times more likely to have acute kidney injury
  • 1.7 times more likely to have an abnormal heart rhythm
  • 1.6 times more likely to have a placental abruption (when the placenta comes away from the womb before birth)
  • 1.4 times more likely to have a caesarean delivery (which are generally very safe, but can increase complications for mother and baby)
  • 1.3 times more likely to have a premature baby.

These complications were more common in women with risk factors for cardiovascular disease. However, assisted pregnancies increased the chances of these complications, whether or not the women had cardiovascular risk factors. Assisted pregnancies also came with increased risk of these complications whether the woman was having a single baby or multiple babies (such as twins or triplets).

On average, the cost of delivering a baby was more for women with assisted pregnancies than for those with unassisted pregnancies ($18,705 versus $11,983). Women were tended to spend longer in hospital after the baby was delivered compared with unassisted pregnancies.

Why is this important?

This is the largest study to date into complications during birth and cardiovascular outcomes in pregnancies following fertility treatment.

Both clinicians and people considering fertility treatment need to be aware of the raised risk of cardiovascular disease and of birth complications. The information will allow them to make an informed decision about treatment. The researchers state, however, that the overall risks associated with fertility treatments are low. For example, for every 10,000 births only 38 people with assisted conception pregnancies had acute kidney injury versus 9 for those with unassisted pregnancies.

Clinicians who specialise in women’s health and pregnancy are generally aware of the increased risk of birth complications associated with assisted conception. However, the risk of cardiovascular disease is less well-known.

A UK report in 2021 showed that many women who died from heart disease during or after an assisted pregnancy had pre-existing cardiovascular risk factors that were not properly assessed before treatment.

Greater awareness, and better health monitoring, could help ensure that cardiovascular diseases and birth complications are successfully managed or avoided in assisted pregnancies.

What’s next?

Guidelines should recognise the risk of birth complications and cardiovascular disease in assisted pregnancies. Women need to know about the increased risks associated with these pregnancies, and have their risk of cardiovascular disease assessed, before they start treatment.

Future studies could explore how to reduce women’s risk of cardiovascular disease before they start fertility treatment. Exercise and diet interventions could potentially reduce birth complications and improve long-term cardiovascular health. In addition, studies greater than 12 months could assess the long-term cardiovascular health of women who became pregnant after fertility treatment.

The study did not compare different types of assisted conception (for example, IVF or drugs to control the release of an egg). Further analyses could explore whether some types of assisted conception carry more risk than others.

This study was based on a US database. Similar studies could assess whether these findings apply elsewhere.

You may be interested to read

This NIHR Alert is based on: Wu P., and others. In-Hospital Complications in Pregnancies Conceived by Assisted Reproductive Technology. Journal of the American Heart Association 2022;11:5

A plain language summary of the paper.

The study has been covered by CNN, NBC News and the Daily Mail.

The Human Fertilisation and Embryology Authority provides information on the risks of assisted conception pregnancy.

More information on fertility treatments is available on the NHS website.

Funding: Authors of the study received funding from the NIHR Transitional Research Fellowship, the West Midlands NIHR Applied Research Collaborations, and an NIHR Professorship.

Conflicts of Interest: The study authors declare no conflicts of interest.

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.

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