Women born in the spring months may start menopause slightly sooner than women born in the fall, according to new research.
The Italian study showed that, on average, women who were born in March started menopause earliest, just before their 49th birthday, while those born in October started latest, about three months after their 50th birthday.
According to The American College of Obstetricians and Gynecologists, in North America the average age of menopause is 51.
Researchers say the results add to growing evidence that environmental factors affecting the fetus during pregnancy may affect the baby's adult life.
In this case, female babies born in the autumn may have developed better and may be born with a larger number of eggs than babies born in the spring. Menopause occurs when a woman completely ends her menstruation, when her ovaries lose their ability to supply eggs.
Spring Baby, Earlier Menopause?
In the study, researchers surveyed nearly 3,000 women attending four different menopause clinics in Italy about their season and month of birth and age at which they started menopause. The results appear in the current issue of the journal Human Reproduction.
They found that the average age of menopause was about age 49 for women born in the spring and almost 50 for women born in the fall.
Researchers say those differences remained significant even after taking other factors that may affect the starting age of menopause, such as age of their first period, weight, smoking status, level of education, and occupation.
Although the seasons may affect women differently in different geographic areas, researchers say the results seem to show that there are notable effects of the month and season of a woman's birth on the length of her fertile life.
They say it's not exactly clear what environmental factors may affect the timing of menopause in a woman before she's born. But possible explanations may include seasonal differences in temperature and sunlight that may affect fetal development. Seasonal factors may also affect diet or exposure to infections in the mother, which may affect the function of the ovaries in females before birth.
SOURCES: Cagnacci, A. Human Reproduction, May 2005; vol 20. News release, European Society of Human Reproduction and Embryology. The American College of Obstetricians and Gynecologists.