On the other hand, having a child in one's teens is not only potentially disruptive for the teen, but generally not great for the child either. Some teens have strong support networks and end up being great parents, and their kids turn out as well as they would have if they'd been born later. But let's face it, statistically, they don't, even after you control for other factors.Here’s the difficult question: Why does it matter how good the child’s life prospects are, so long as they are on net positive? The response would seem to be that the child’s life prospects are worse than if the child had been born under different circumstances, and so the child is in some sense harmed. But that logic doesn’t fly, because the particular person that results from one accidental teen pregnancy only exists under that circumstance. If the teen mother had abstained from sex, that child would simply never have come into being, so it makes no sense to say the child is “harmed” by the teen mother’s having gotten pregnant. Even if we assume that the teen mother would, if she hadn’t gotten pregnant in her teens, have had another child later in life under better circumstances, that child would be a different person, resulting from a different egg and different sperm, with a different genetic make-up and different characteristics and life experiences.
Of course, there are many good reasons to be concerned about the children of teen mothers, most of them relating to the effects such children may have on other people. If they are more likely to be criminals who predate on the rest of us, for instance, that’s obviously a relevant consideration. The teen mother herself is also likely to have a more difficult life; likewise for the father who is obliged to make child-support payments. But holding all those other-affecting factors constant, the question is whether the relative well-being of a child itself should make a difference to our judgments about the desirability of teens becoming parents.
If we take an average utilitarian position (that is, we should maximize the average rather than the total utility of society), then a concern with the relative well-being of the child of a teen mother makes sense. But adopting the average utilitarian position has some other rather unsettling implications – among them, the conclusion that you ought not bring any child into this world whose expected utility is lower than the society’s average utility, even if the child’s expected utility is strongly positive. This has implications for many, many children other than those born to teen mothers! (The total utilitarian position has problems as well, of course.)
My tentative take is that if we assume there is no “replacement child” later when a teen avoids having a child now, then the relative quality of the life of the child of a teen mother is not relevant; my reaction thus tracks that of the total utilitarian (thus possibly exposing me to some version of the Mere Addition Paradox). If, on the other hand, there is a “replacement child,” then both average and total utilitarianism give the same answer: it’s better to wait. However, the reason is not that the child of a teen mother is somehow “harmed” by her having given birth to him. The reason is that, if you imagine yourself having an equal chance of having either hypothetical child’s life, you would rather have that of the child born under better circumstances. But I wonder if that’s really the implicit reasoning of people who push the message that teen pregnancy is bad for the resulting child.
If I'm going to keep pondering issues like these, I really need to bump Derek Parfit to the top of my reading list.