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The Boston Globe

Health & wellness

Health Answers

Menopause and worrying about birth control

Q. When can a woman going through menopause stop worrying about birth control?

A. Menopause “officially” occurs 12 months after a woman’s last menstrual period — a diagnosis that can only be made after the fact. It is when a woman’s fertility permanently ends, and usually occurs in the 40s or 50s; the average age in the United States is 51. The years leading up to menopause are a time when fertility drops sharply and periods continue but become less frequent and more irregular.

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“A large number of unplanned pregnancies occur in women in their 40s,” says Sarah Crane, an attending physician in OB/GYN at Cambridge Health Alliance. A woman may think she’s infertile or mistake missed periods for menopause when she’s actually pregnant.

Crane advises sexually active women to continue using birth control until their doctor has established that they are no longer fertile. Women who are healthy nonsmokers can safely take low-dose birth control pills into their 50s, she says, and many women opt for intrauterine devices (IUDs). A blood test for follicle-stimulating hormone (FSH) is used to determine that a woman can no longer get pregnant. “This hormone is high in a woman who no longer has any viable eggs,” Crane says. Some doctors advise stopping birth control at an arbitrary age, such as the mid-50s, when a woman is almost certainly not fertile.

But women who have natural pregnancies late in life have cause to celebrate: Getting pregnant at 45 or older without assisted reproduction has been linked to greater longevity.

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