Fertility, Maternal Age and Child Development

In suggesting alternatives to the status quo of high-status women delaying childbirth further and further, Robin Hanson notes that, unlike advanced paternal age, advanced maternal age does not correlate with poor learning and social outcomes in children (in fact, older mothers had children who scored higher).

In all cases, we find evidence that children of older mothers have better outcomes. Not only do children born to mothers in their twenties do better than children born to teen mothers, but children born to mothers in their thirties do better than children born to mothers in their twenties. However, when we control for other socioeconomic characteristics, such as family income, parental education and single parenthood, the coefficients on maternal age become small and statistically insignificant. The only exception is an index of social outcomes, which is positively associated with maternal age, even controlling for socioeconomic factors. For cognitive outcomes, young motherhood appears to be a marker, not a cause, of poor child outcomes.

That may be, but Hanson also states that women drastically underestimate their fertility in later life.

The average woman is born with around 300,000 eggs […] with just 12 percent of those eggs remaining at the age of 30, and only 3 percent left by 40. […]

It is clear that there’s a very rapid loss in the number of eggs available as women age and that the smaller pool of [older] eggs is also more likely to contain a higher proportion of abnormal eggs. […]

It’s important to remember that even 30,000 or so eggs remaining at the start of your 30s is still a lot. In addition, the quantity and quality of eggs are just two factors affecting fertility: […] lifestyle factors such as stress, smoking and being overweight can have an increasingly negative impact on fertility as you get older.

2 thoughts on “Fertility, Maternal Age and Child Development

  1. Paul

    It should also be remembered however that the cause of 30% of infertility among women remains completely unknown to science – this factor by far outweighs any consideration of the number of eggs remaining – after all only one is released at a time!

  2. Lloyd Morgan Post author

    I did feel the statement of the number of eggs available was fairly impotent.

    As the reproductive endocrinologist (Robert Stillman) states in the article:

    “One might be able to argue whether there are 12 percent remaining at age 30 or 22 percent or even 40 percent, but it is still clear that there’s a very rapid loss in the number of eggs available as women age.”

    Yes, a rapid loss, but they definitely aren’t “running out”.

    Underestimating fertility is an issue, but it’s not an issue because of the number of eggs available at any given age. There are more important factors to deal with, like you say. Especially the unknowns.

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