Soon-to-be-released government figures show a major cultural shift since the days of “shotgun weddings” aimed at avoiding family embarrassment. With marriage on the decline, the shift is helping redefine the traditional notion of family.

“The emergence of cohabitation as an acceptable context for childbearing has changed the family-formation landscape,” said Christina Gibson-Davis, a sociology professor at Duke University. “Individuals still value the idea of a two-parent family but no longer consider it necessary for the parents to be married.”

Still, she cautions that children in cohabiting households may face more difficulties growing up if their unmarried parents are at higher risk of breaking up.

In all, the share of unmarried couples who opted to have “shotgun cohabitations” — moving in together after a pregnancy — surpassed “shotgun marriages” for the first time during the last decade, according to a forthcoming paper from the National Center for Health Statistics, part of the Centers for Disease Control and Prevention. The trend was affirmed by three demographers who conducted separate research on the topic.