Obesity, high blood pressure, hypertension, and diabetes are known stroke hazards, however they do not entirely explain women’s increased risk of stroke. Previous research on the relationship between infertility, miscarriage, and stillbirth and long-term stroke risk was equivocal.
To fill in the gaps, this study sought to examine the relationship between infertility, miscarriage, and stillbirth and the risk of fatal and non-fatal stroke, as well as the type of stroke.
The researchers examined data from 27 studies from the InterLACE collaboration, which collects data on reproductive health and chronic illness. The research includes data from eight studies from seven nations (Australia, China, Japan, the Netherlands, Sweden, the United Kingdom, and the United States).
Infertility, miscarriage, and stillbirth were all investigated using questionnaires. Non-fatal stroke data was also discovered using self-reported questionnaires or hospital records. Hospital data were utilised to identify fatal stroke patients and stroke subtypes (haemorrhagic or ischaemic).
The research comprised around 620,000 women ranging in age from 32 to 73 at the start.
Of them, 275,863 women had both non-fatal and fatal stroke data, 54,716 only had non-fatal stroke data, and 288,272 only had fatal stroke data. Among them, 9,265 (2.8%) women had their first non-fatal stroke at the age of 62, while 4,003 (0.7%) suffered a fatal stroke at the age of 71.
Women under the age of 40 who had a non-fatal stroke were excluded because they may have suffered a stroke before a history of infertility, pregnancy loss, or stillbirth could be established. Several other factors that may have impacted the results were considered, including ethnicity, weight, lifestyle, and underlying diseases.
The study discovered that infertility, miscarriage, and stillbirth were all related with an elevated risk of stroke, particularly recurrent miscarriages (three or more) and stillbirths.
Women with a history of infertility had a 14% greater risk of non-fatal stroke than women without a history of infertility.
Miscarriage was also linked to an 11% increased incidence of non-fatal stroke in comparison to women who had not experienced a miscarriage. The risk rose with the number of losses a woman experienced: one, two, and three miscarriages resulted in a 7%, 12%, and 35% increase in stroke risk, respectively.
Women who had three or more miscarriages had a 37% and 41% higher risk of non-fatal ischemic and haemorrhagic stroke, respectively. Similarly, for fatal ischemic and hemorrhagic stroke, three or more miscarriages were associated with an 83% and 84% increase in risk, respectively.
A history of stillbirth was linked to a 30% increased risk of non-fatal stroke, and women who had many stillbirths (two or more) were almost 80% more likely to have a non-fatal ischemic stroke.
The study also discovered that recurrent stillbirth was related with a 40% increased risk of fatal stroke.
Endothelial dysfunction (narrowing of the heart’s blood channels) may explain the higher risk of stroke in women with a history of recurrent stillbirth or miscarriage, according to the researchers.
Lifestyle, infertility and miscarriage
However, studies also imply that unhealthy lifestyles (such as smoking or obesity) are linked to pregnancy loss and infertility, which may lead to an increased risk of stroke.
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Because this is an observational research, it cannot determine a causation. Alternative limitations of the study include the fact that information was gathered using questionnaires; the effects of other therapies were not investigated due to inadequate data; and definitions of infertility, stillbirth, and miscarriage may change among studies.
Nonetheless, this was a big, well-designed study, and the results remained mostly unaltered after additional analyses, indicating that the findings are sound.
“Having a history of recurrent pregnancy loss may be considered as a female-specific risk factor for stroke,” the researchers write.
They also advise that early monitoring of women with a history of miscarriage or infertility, as well as promoting healthy behaviours, may assist to reduce their risk of stroke later in life.
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