In some cases, the father of the child is the husband of the teenage girl. The conception may occur within wedlock, or the pregnancy itself may precipitate the marriage (the so-called shotgun wedding). In countries such as India the majority of teenage births occur within marriage.
In other countries, such as the United States and the Republic of Ireland, the majority of teenage mothers are not married to the fathers of their children. In the UK, half of all teenagers with children are lone parents, 40% are cohabitating as a couple and 10% are married. Teenage parents are frequently in a romantic relationship at the time of birth, but many adolescent fathers do not stay with the mother and this often disrupts their relationship with the child. Research has shown that when teenage fathers are included in decision-making during pregnancy and birth, they are more likely to report increased involvement with their children in later years. In the U.S, eight out of ten teenage fathers do not marry their first child's mother.
However, "teenage father" may be a misnomer in many cases. Studies by the Population Reference Bureau and the National Center for Health Statistics found that about two-thirds of births to teenage girls in the United States are fathered by adult men age 20 or older. The Guttmacher Institute reports that over 40% of mothers aged 15–17 had sexual partners three to five years older and almost one in five had partners six or more years older. A 1990 study of births to California teens reported that the younger the mother, the greater the age gap with her male partner. In the UK 72% of jointly registered births to women under the age of 20, the father is over the age of 20, with almost 1 in 4 being over 25.