Trends in women's reproductive events reflect major social and lifestyle changes

An international study has revealed the age at which women experience major reproductive events, such as their first period or giving birth, has changed significantly over time.

University of Queensland School of Public Health Professor Gita Mishra said the results of the InterLACE Study highlighted potential lifelong health implications.

"On average, women experienced menarche (first period) at age 12.9 years, their first birth at 25.7 years, and natural menopause at 50.5 years," she said.

"Women born from 1970 onwards experienced menarche one year earlier than those born before 1930, down from 13.5 to 12.6 years.

"Compared with women born in the 1940s, women born from 1970 onwards were having their first birth 2.5 years later, up from 24.8 to 27.3 years.

"And the percentage of women who had no children also increased markedly from 14 to 22 per cent."

Professor Mishra said it was important for women to understand the impact of these timing changes.

"The timing of reproductive events is linked to the risk of adverse hormone-related outcomes for women, such as earlier menarche with increased risk of diabetes and cardiovascular disease.

"By benchmarking the reproductive characteristics of different groups of women, we can not only better understand their reproductive health needs today but also their risk of chronic diseases in later life."

The research also identified relationships between reproductive events and social and environmental changes.

"The study covers the first generation of women to have access to oral contraceptives, and they also saw major changes in education levels and workforce participation," Professor Mishra said.

"Women who had college/university education had fewer children, had their first child later, and experienced later menopause (50.6 years) than women with less than 10 years of education (49.9 years)."

Professor Mishra said the findings could help guide future health services policy, planning and delivery.

"More broadly, it helps women be aware of how their reproductive characteristics are linked with long-term health outcomes."

The InterLACE Study analysed data from more than half a million women in 10 countries.

The data will now be used to quantify the increased risk of chronic diseases associated with specific reproductive characteristics.

The research is published in Human Reproduction.