NEW YORK (Reuters Health) - Women who had their first menstrual period at a relatively later age may have an easier time giving birth to their first child, a new study suggests.
The study, of more than 3,700 first-time moms, found that the older a woman was when she had her first period, the less likely she was to need a C-section or a vaginal delivery using forceps or a vacuum pump.
Among women who'd started their periods at age 12 or younger, 32 percent required a C-section or instrument-assisted delivery.
Those rates were 30 percent, 29 percent and 27 percent among women who'd begun menstruating at the ages of 13, 14 or 15 or older, respectively, according to findings published in the British obstetrics journal BJOG.
The study results do not mean that women who began their periods relatively early should be worried about labor and delivery, according to Dr. Gordon C. S. Smith, head of obstetrics and gynecology at Cambridge University in the UK and the author of the study.
Instead, he says, the main contribution of the study is that it may help explain why women who delay childbirth until a later age have a higher risk of difficult delivery.
It's known that older women have a higher rate of operative delivery -- either by C-section or with the help of forceps or a vacuum device. But the reasons have not been fully clear.
According to Smith, his findings support the theory that the longer a woman is exposed to the hormonal fluctuations of menstruation, the greater the likelihood of impaired uterine function.
The uterine muscles are "profoundly controlled" by estrogen and progesterone, Smith explained in a written statement provided to Reuters Health, and it's possible that prolonged hormonal stimulation causes some amount of dysfunction in those muscles -- leading to more difficult labors and a higher rate of unplanned C-sections and instrument-assisted delivery.
