Ask the Experts – Heredity and Fertility
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Q.
My grandmother had a daughter (my mother) pretty late in her life – I believe she was 42! Can I count on being fertile at this late age?
A.
Aging of the egg is a complex event. It is possible that the eggs of mothers and daughters age similarly, and that some of what we see as age-related infertility may be genetically determined. We have not identified any definitive research, but there is suggestive evidence that late age fecundity is passed from one female generation to another.
It is clear that the age at menopause runs in families. The average age at menopause is 49, but a few women enter menopause in their 20s or 30s and some in their 50s or 60s. The strongest predictor of a woman’s age at menopause is her mother’s age at menopause.
In certain population clusters there are women that show very high natural fecundity. In these groups, the women are closely related, and they continue to attempt conception into later years. Very high natural fertility rates can occur into the late forties.
There are some chromosomal abnormalities that can cause premature menopause that can be inherited. An example is a Turner’s mosaic, where a woman is missing a piece of her X-chromosome. This problem is associated with premature menopause, and can be passed from mother to daughter.
Many non-genetic factors determine late-life fertility, such as use of birth control, degree of sexual activity, and medical problems that affect the uterus and ovaries. Some of these factors are determined by personal choice, and some are events that occur naturally. Many are not genetically determined.
The determinants of fertility are complex; many factors play a role in fecundity. Until dedicated research studies examine the question of whether late life fertility is heritable, we would have to say that we are not sure of the strength of the genetic relationship. There likely is a genetic determinant, but not necessarily one on which you can depend.
– Philip Chenette, MD
