Scientists have found an association between so-called reproductive factors - such as having children and breastfeeding - and a woman's risk of death.

The study, published today in the journal BMC Medicine, also found that starting menstruation later in life (above the age of 15), and using oral contraceptives, were linked with a reduced risk of death.

The international team behind the work – led by epidemiologist Dr Melissa Merritt from Imperial College London, say the insights may help scientists develop strategies to improve women’s health.

The scientists analysed data from 322,972 women across 10 countries (including the UK, France, Germany and Sweden), with an average age of 50. The data came from the European Prospective Investigation into Cancer and Nutrition (EPIC) study.

 At the start of the study, participants completed questionnaires and interviews about diet, lifestyle characteristics and medical history.  Each woman was followed for an average of 12.9 years, and their risk of death calculated over this period. In this time there were 14,383 deaths overall, which included 5,938 deaths from cancer and 2,404 deaths from circulatory system diseases.

Previous studies have suggested a link between individual reproductive factors (such as age of first period or whether a woman breastfed) and risk of specific diseases. However in the current study, the team compared a host of reproductive factors with risk of death from several common conditions, such as breast cancer, stroke and heart disease.

The team found that women who had given birth had a 20 per cent reduced risk of death than those who had not.

Within the former group, those who had given birth early or later in life had a higher risk of death compared to those who gave birth between the ages of 26 and 30 years old. It was also found that there was a reduced risk of death (8 per cent) in women who had breastfed compared to those who did not.

Women that started menstruating at the age 15 or older had a reduced risk of death compared to those that started when they were less than 12 years old. A reduced risk was also seen in women that had taken oral contraceptives (and had never smoked or were former smokers).

The risk of death from cancer was lower in those that had given birth compared to those that had not. Within this group, the risk was reduced even further in women that gave birth to two or three children in comparison to those who had one child.

When looking at risk of death from circulatory diseases, such as heart disease and stroke, it was found that the following characteristics were associated with a reduction in risk: having given birth, breastfeeding, and starting menstruation at the age of 15 or older. A sub-analysis found a link between women that have given birth and breastfed and a reduced risk of death from ischaemic heart disease.

The team controlled for factors that could affect mortality such as body mass index, smoking habits and levels of physical activity.

Dr Merritt, from Imperial’s School of Public Health, said:  “We observed that several reproductive factors were associated with a significantly lower risk of death. These factors may influence the long-term health of women.”

“Hormonal mechanisms may explain the lower risk of death that we observed with breastfeeding, having given birth and using oral contraceptives, as these factors are associated with changes in hormone levels.

 “Because this was an observational study, the research does not show that these factors (such as breastfeeding and childbirth) directly reduce the risk of death. Rather, the research suggests that there may be a relationship between these factors and risk of death. Further studies are needed to explore this relationship, and the mechanisms that may link these risks.”