Young women across the whole of the less economically developed world have children at very young ages as happened in the west before industrialisation (and equal opportunities) came into play. We don't condemn rural peasant cultures where marriage and motherhood commence shortly after puberty, and even if we wish it were not so, then generally we appreciate the reasons for it - shorter life expectancy, lack of state social welfare provision, lack of health care, lack of education, lack of alternative lifestyle choices etc.
Here in the west tho single teenage motherhood is viewed by those not involved as a bad thing even when there are no economic costs to society - generally because of the notion that very young mums are damaging their own potential life chances and consequently those of their infants.
But as we all know, over the past couple of decades it has become harder not easier for people to climb out of the socio-economic position they have been born into. A young girl born poor has little chance of becoming not-poor whether she becomes a teenage mum or not. In fact, research has found that poor teenage mums have very similar earnings trajectories to similarly poor young women who wait until their mid or late 20s to begin a family. These days having a baby at 14/15/16/17/18 does not economically disadvantage either the mother or the child in comparison to older poor mums.
Given the increasing likelihood in western societies that a woman will at least partially raise her children alone isn't it economically sensible for a poor young girl to choose to have her children while she still has the financial and practical support of her family rather than wait until she has no choice than to go it entirely alone?