Women are at greater risk of stroke, the more miscarriages or stillbirths they've had

New research shows women who have had a miscarriage or stillbirth, have an increased risk of stroke – when blood can’t get to the brain, because of a blocked or burst artery. That risk increases with each miscarriage or stillbirth.

Trying to establish this link is difficult because it requires following a large number of women over a long period of time and having reliable data on women’s experiences. Our study, published by the British Medical Journal today, is the first to conclusively show the link between pregnancy loss and stroke.

Many women are unaware their experiences during pregnancy can be an early marker of later health dangers. Our findings show their doctors should be alert to their increased risk.

It’s possible infertility, miscarriage, and stillbirth could increase stroke risk because of other health issues. These could include endocrine disorders (low oestrogen or insulin resistance), inflammation, problems with endothelial cells that assist in blood flow, psychological disorders, unhealthy behaviours (such as smoking) or obesity.

Heartbreak then stroke risk

Our research is based on pooled data from 618,851 women who took part in eight separate studies in Australia, China, Japan, Netherlands, Sweden, the United Kingdom and the United States.

The women were aged between 32 and 73 when they were first enrolled in the studies and were followed up for an average of 11 years.

The study showed that over the time they were studied, 9,265 (2.8%) women had at least one non-fatal stroke and 4,003 (0.7%) women had a fatal stroke. Overall, 91,569 (16.2%) women had a history of miscarriage while 24,873 (4.6%) had a history of stillbirth.

Among the women who had ever been pregnant, women who had reported a miscarriage had a 11% higher risk of a non-fatal stroke and 17% higher risk of a fatal stroke compared with women who have not had a miscarriage.

The risk increased with each miscarriage, so that women who had three or more miscarriages had a 35% higher risk for non-fatal stroke (from incidence rate of 43 per 100,000 “person years” to 58 per 100,000) and an 82% higher risk in fatal strokes (from 11.3 per 100,000 person years to 18 per 100,000) compared with women who had never miscarried.

Stillbirth also significantly increased the risk of stroke.

Among women who had ever been pregnant, women who had a history of stillbirth had a 31% higher risk of non-fatal strokes (from an incidence rate of 42 per 100,000 person years to 69.5 per 100,000) and a 7% higher risk of fatal strokes.

Again, the greater the number of stillbirths, the higher the risk of later strokes, with women who had had two or more stillbirths having a 26% higher risk of fatal strokes (rising from 11 per 100,000 person years to 51.1 per 100,000).

The study is the first to show links with stroke subtypes: stillbirths were linked to non-fatal ischaemic (blockage) stroke or fatal haemorrhagic (bleeding) stroke; miscarriages were linked to both subtypes.

Our study strengthens findings from a previous systematic review that found similar results but showed limited evidence linked to stroke subtypes.

Of the possible explanations for these links, problems with endothelial cells (which control vascular relaxation and contraction as well as release blood-clotting enzymes) might lead to pregnancy loss through problems with the placenta. These problems also relate to how blood vessels dilate and get inflamed or blocked during stroke.