15, sez Louie Helm.
In terms of health outcomes for mother and child, that is.
I don't know how large these effects are. They don't seem huge. Other prudential arguments for later pregnancy may be stronger.
But this further reinforces my view that teenage pregnancy is not as bad as it's usually seen as. It's got a lot going for it, even.
Although it's completely outside the societal norm these days, having a child at 15 leaves a woman free to immediately start her career after finishing college because her child will be entering school right as she leaves it. Assuming the mother enrolls in an elite online high school program, she could take one summer off to deliver and never miss a beat in her academic (and real) career.
Is that last sentence naive? Of course, how much help she has has got to be a big factor.