Teen pregnancy is not a new thing, but society is a bunch of people who know that raising children is hard work and without the right skills, support or finances it becomes a lot harder and poorly raised children can sometimes become a threat to society. So, society frowns on some people (,not just teenagers,) becoming pregnant and will try to discourage them by holding opinions or if daring enough with sharp comments or glaring looks. Some teenagers have done a good job of parenting because they did the hard work and had the necessary support.
Children turn your life upside down at what ever age you have them. If the reason for getting pregnant is poor planning, then a lot of personal growth will be required very quickly. The best and worst parenting is not done by any one demographic, it is the work of caring and supportive or mean and selfish people.