Month of birth influences menopause age - study

A woman's month of birth determines more than just her star sign, it also influences the age when menopause begins.

Scientists from the University of Modena in Italy have discovered that women born in March have the earliest age of menopause, while those with an October birthday have the latest.

"The age of menopause is influenced by the season in which the female is born," said Dr Angelo Cagnacci, an associate professor of obstetrics and gynaecology at the university.

The findings, reported in the journal Human Reproduction, support the theory that environmental factors before birth have an impact on the baby's adult life.

"It shows prenatal life is important for future adult life. Things that happen before delivery, during pregnancy, may determine many things in adult life, including when reproduction ends," said Cagnacci.

In a study of 3,000 Italian women, the researchers said there was an 18-month difference in the age of menopause depending on the month of birth.

After controlling for factors such as smoking, weight and age at puberty, which can affect menopause, the researchers said women born in October reached the menopause at 50 years and 3 months, compared to 48 years and 9 months for those born in March.

They do not know why, but suspect temperature and sunlight could influence the growth of the foetus in the womb and its later reproductive life.

They added that the effects of the months on the age of menopause could be different in other parts of the world because of seasonal changes.

"Our present data seem to indicate that women born in autumn develop better during their prenatal life and are born with a higher number of oocytes (eggs) than women born in spring," said Cagnacci.

"An alternative explanation may be that early mortality is highest among children born in autumn, thus selecting the fittest for survival, although other studies do not support this hypothesis," he added in a statement.

The scientists are now looking at whether a woman's birth month has an impact on her psychological profile and moods.

"There is a clear seasonal modulation," Cagnacci said.