31. There are biological consequences.

It is never entirely your decision as to when you will marry or have children, but to the extent that it is, there are some important facts of life to keep in mind. There is a price to pay for delaying adulthood and marriage (see Reasons 12 and 15) that goes beyond the psychological cost of graduate school (see Reason 10). For women, fertility begins to decline before the age of 30, and for men the decline begins in the late 30s. For women over 35, fertility-treatment effectiveness also declines.

Because the road through graduate school to a secure job and income is such a long and uncertain one, graduate students have good reason to wait before starting a family. Of course, the longer people wait to have children, the fewer children they can have. And if they wait too long, it can be difficult to have any children at all. This is not an issue that usually crosses the mind of someone considering graduate school, but it should. The subject of a 2002 cover story in Time magazine, the grief that Sylvia Ann Hewlett calls the “crisis of childlessness” has affected a generation of successful people who made career a priority over family. To make matters worse, graduate school has the effect of putting off both family and career.