When a child is born in Philadelphia, the mother's name is listed on the birth certificate. If the father is present or the mother wishes to name the father, his name will also be included. Some women choose not to name the fathers, precluding them from receiving child support and from the fathers having access to or custody of their children. If no father is listed, authorities need not get the father's consent to give up his parental rights to the child if the mother wishes to put the child up for adoption. What that really means is that mothers need not ask or inform the father of their children that they are putting the children up for adoption.
In order to give fathers notice that their children are being put up for adoption, 33 states have developed putative father registries, but these registration systems have far from solved the problem.
One of the problems associated with this system is that each state has a different registration process and requests different pieces of information. If a man doesn't register in all the state's in which a former partner could possibly give birth, he may be out of look if the woman chooses to put the child up for adoption.
Of course, the stereotype of men who conceive children outside of marriage are seen as bad or nonexistent parents, men who have no interest in raising a family, and men that are too oblivious to even notice that their partners are pregnant. Some men, however, would gladly take on the responsibilities of being a full-time father if they only knew that their former partners were pregnant and looking to give the child up.
Source: The Atlantic, "Sex and the Single Man: What If Your Partner Has a Kid?" Kevin Noble Mallard, April 21, 2014