I'm coming rather late to this discussion, but I think the argument that young mothers should be "punished" financially or in any other way is short-sighted and vindictive, and completely counter-productive.
1. It won't discourage young mothers. I hardly think that most young mothers get pregnant just because they think their choices will be subsidized. Oh goodie! Free government handouts! And meantime, I can miss the rest of my adolescent years and be stigmatized by society
I therefore hardly think that removing subsidies that help children of young, unwed mothers would be a sufficient deterrent to drop the birth rate in that population.
2. Arguing that young mothers are likely to have children with health problems is exactly WHY we should provide services for them and their children - spending a few dollars up front to help a mother continue her education and get a good job, or to take care of her baby's health is going to pay off in the long run - it's a lot cheaper than permanently subsidizing them on welfare because she had to drop out and can't get a good job, or taking care of a sick individual throughout his or her lifetime because they didn't have proper preventive care as an infant. Add to this the research that chronic stress (such as financial hardship, having a depressed or anxious parent, inconsistent caregiving environment, etc.) early in life increases the likelihood of mental and physical health problems down the road (that cost society in terms of public services and lost wages) and I think that cutting young mothers a break and making their lives easier and their children healthier is a sound investment. Not to mention that it cuts down on the intergenerational transmission of poverty by making it less likely for the baby to suffer cognitive and emotional disorders that would increase his/her chance of being a young parent and/or dropping out of the education system at some point.
If you really want to solve the problem, shame our government into funding comprehensive sex education that actually has clinical data showing that it works better than abstinence-only education, and make sure all teenagers, especially women, have access to birth control.
Failing that, punishing them after the fact does nothing to alleviate the problem, and in fact only perpetuates social problems like crime, poverty, and physical and mental health problem.
We should do all we can to help people make good choices within their current circumstances, not punish them for having made poor choices or having been unlucky in the first place.
Oh, and incidentally, I hope that if you, crusader, ever make a mistake that you are shown the same compassion you would extend to others.