Teenage motherhood for the first child, sure. But women can continue having children into their 40s without significant difficulty. No guarantee that the firstborn will be the one who thrives relative to younger siblings particularly if the mother is an inexperienced or impoverished mom as a teenager.
So you really need to look at the median motherhood age, not the first opportunity of pregnancy.
Teenage motherhood for the first child, sure. But women can continue having children into their 40s without significant difficulty. No guarantee that the firstborn will be the one who thrives relative to younger siblings particularly if the mother is an inexperienced or impoverished mom as a teenager.
So you really need to look at the median motherhood age, not the first opportunity of pregnancy.
Indeed, and there was high infant mortality when teenage motherhood was the norm as well.