If a women is married and has an affair who pays child support?

To clarify, if you mean a woman has had an affair and become pregnant? If this is the case, and the husband is aware of it, he can order a paternity test to determine if the child is his or not. If it is not, as far as I know, the woman can go after the man who fathered the child for financial support. Support obligations only belong to the actual biological father OR a father who has legally adopted a child. There is a whole moral issue though - if the parents are staying together, does the husband want to alienate this child by not supporting it and how would he live in the same house and not support it? So really it depends on if the couple stays together. If they don't, the husband has NO obligation to support the child.