This paper expands the migration-fertility linkage literature by examining the fertility impact of temporary migration in Hubei, China. The central hypothesis is that temporary migration affects migrants' fertility through a detachment process: The separation of temporary migrants' actual residence from their de jure residence creates a loophole in family planning administration, weakening the social control over their fertility. The analysis of annual order-specific births since 1979 suggests that temporary migrants exhibit significantly higher probabilities of having a second birth than permanent migrants and nonmigrants once type of residence is controlled for: rural-rural temporary migrants have the highest fertility among all groups examined. The results lend support to the detachment hypothesis while indicating a strong antinatal impact of urban residence. Rural-urban temporary migrants are not the ones to blame for increases in outplanning births in contemporary China, but their fertility would have been lower if there had been no detachment. Rural-rural temporary migrants are actually the escapees of the one-child-per-family policy.