An early menopause and never giving birth both increase a woman's risk of heart failure, new research has shown.
The association is thought to be linked to the way sex hormone levels are affected by menstruation and pregnancy.
Scientists analysed data on 28,519 post-menopausal women taking in the Women's Health Initiative study, a major US investigation looking at causes of death and chronic illness in older women.
Over an average follow-up period of 13.1 years, 5.2% of the women were admitted to hospital with heart failure, a condition that results from the heart being too weak to pump blood efficiently.
Early menopause, which occurs when a woman reaches the end of her reproductive age unusually soon, correlated with a statistically significant increased risk of heart failure.
The association was more pronounced when an early menopause occurred naturally rather than as a result of surgical removal of the ovaries.
In the UK, the average age for a woman to reach the menopause is 51. Around one in 100 women experience a premature menopause before the age of 40.
Women who never gave birth were also found to be more at risk of diastolic heart failure, a specific problem affecting the left side of the heart.
Lead researcher Dr Nisha Parikh, from the University of California at San Francisco, said: "Our finding that a shorter total reproductive duration was associated with a modestly increased risk of heart failure might be due to the increased coronary heart disease risk that accompanies early menopause.
"These findings warrant ongoing evaluation of the potential cardio-protective mechanisms of sex hormone exposure in women."
Commenting on the research, published in the Journal of the American College of Cardiology, US heart expert Dr Nandita Scott said the study highlighted the heart-protective properties of the female sex hormone oestrogen.
Dr Scott, from Massachusetts General Hospital, said: "There also remain many unresolved questions including the mechanisms of oestrogen's cardioprotective effect, making this truly a work in progress.
"Altogether, these findings raise interesting questions about the cardiometabolic effects of sex hormone exposure over a woman's lifetime and continue to raise important questions for future research."