Increases in union stability and non-union childbearing during the latter half of the 20th century produced substantial increases in the prevalence of step-families. Research on step-family fertility in several European countries and the United States show that, net of a couple’s combined number of children (hers, his and theirs), birth risks are elevated when the child is the couple’s first or second.
These patterns have been interpreted in terms of unique values of first and second shared children that overcome costs of rearing larger numbers of children in stepfamilies. Such inferences require that all births are wanted or that unwanted births are as likely for couples with as for those without stepchildren.
Analyses of several European fertility and family surveys show that previously observed patterns of stepfamily childbearing are replicated in desires for another child, providing stronger support for motivational explanations of childbearing patterns in step-families.