Why are so many teenagers pregnant?

I am a labor and delivery nurse and I am shocked and saddened at home many teenagers are having kids, and not 18 and 19 yr olds. This past weekend at my hospital 9 babies were born to teen age moms all under the age of 16. Many of the kids that come in are 14 -16 yrs old. How did we as society fail these kids. I noticed a huge trend is if one of the friends gets pregnant many of the others in the circle are pregnant with in months. One of the girls that delivered this weekend was 15, 3 of her close friends were also pregnant. They spent one whole afternoon changing and dressing the baby up and taking pictures like they were playing house. If we mention feeding they giggle like children. If you cant say feeding you shouldn't have babies.