When a child is born to a married couple, a legal presumption arises that the husband is the child's father. The same is not true with unmarried couples. Establishing paternity is important for unmarried couples in the event they break up and a parent seeks custody or child support, for inheritance purposes, and in a variety of other circumstances.

If the parents get married after the mother becomes pregnant but before the birth, the husband's paternity is presumed in the same manner as if the parents were married at the time of conception. If the parents marry after the child is born, they can sign a legitimation form, which grants the same rights as if the parents were married at the time of birth.

Even if parents never marry, paternity can be established voluntarily when the parents are certain of the father's identity. In such cases, they may sign a legal form called a voluntary acknowledgement of paternity, or something similar, and then file the form with the court or appropriate state agency. Executing this voluntary acknowledgement can be done right in the hospital following the child's birth, or any time thereafter. The father's name is then included on the child's birth certificate.

Even if a voluntary acknowledgement is not signed, the parties may later enter into an agreement with the help and advice of their attorneys that establishes the father's identity and resolves custody and support issues.

If neither of these voluntary procedures is an option, legal action may be necessary. A mother may file a paternity action to establish that the man she believes to be her child's father in fact is, or, if the mother is receiving public assistance, the state may initiate the action in order to recover its costs from the father. The putative, or probable, father's presence in court will be demanded, and he may be required to submit to DNA testing if he contests his paternity. Genetic blood test results are usually available within a few weeks, and they can establish (or negate) paternity with about 99 percent accuracy. If paternity is established in this manner, the court will enter an order regarding the father's paternity. The father then becomes legally obligated to pay child support according to the state's guidelines, which are generally based on both parents' incomes and the needs of the children.