Starting menopause is a lot like starting your period. Its arrival is heralded by years of funny changes (from breast buds and arm pit hair on the one end, to fatigue and flat-lining libido on the other). No matter how many of your friends and sisters have gone before you, it's stupefying when menopause happens to you.
The surprise factor is likely because: (a) there is no set age by which menses or menopause is supposed to come and (b) our society has a lovely way of repressing reproductive health discussion and education.
It turns out, however, that menopause is, for the most part, fairly predictable. So there's no reason to be shocked if "the change" has finally caught up to you. As a baseline, the National Institute on Aging says the average U.S. woman will stop menstruating by age 51. Many women have their last period sometime in their 40s and even later in their 50s.
The predictability comes in here: the onset of your menopause might have something to do with the onset of your mother's menopause.
The research still isn't entirely conclusive on this relationship, but there have been several studies that hint at a possible connection. One study from the Journal of Clinical Endocrinology and Metabolism showed that half of the variations in menopausal onset among women they studied could be attributed to genetics. They studied 2,000 women from the famous Framingham Heart Study with the aim of determining heritability.
Another such study from the European Journal of Obstetrics & Gynecology and Reproductive Biology suggests that early menopause age can be inherited. In their study of over 500 women, the odds of going through an earlier menopause were significantly higher for women whose mothers had also stopped menstruating early (more than six times as likely when compared to women whose mothers had gone through a later menopause).
The reasoning behind this connection isn't entirely clear yet, however, that doesn't stop doctors from inquiring about a family history during the full menopause work-up.