Background: In a modern society with massive long-distance migration due to rapid development of transportation infrastructure, spousal separation has a substantial and cumulative effect on marital fertility (Menken 1979) due to not only lower intercourse frequency, but also factors affecting fertility in both the destination and origin locations.

Objective: This paper investigates the effect of spousal separation on marital fertility for Chinese internal migrants and international migrants to the US.

Methods: Using data from the Chinese International Migration Project, I jointly model the first, second and third births, and spousal separation applying event-history techniques and controlling for unobserved heterogeneity. Time-varying information on both partners’ occupations is incorporated to capture the changes in their socioeconomic status.

Results: The results show that the first two births are disrupted by spousal separation. Reunification does not lead to higher fertility but rather implies lower fertility. Moreover, there is a tendency for couples who are separated due to the migration of one partner to also have higher fertility levels.

Conclusions: Concerns regarding the dramatic rise in migrant births after family reunification are not empirically grounded. Couple separation is related to a traditional division of labour. Furthermore, the correlation between migration and fertility mainly comes from the selectivity of household income.

Contribution: This paper sheds light on the effects of migration-related changes in couples’ living arrangements on fertility, analysed by birth order in under-researched contexts: China-US migration and internal migration from Fujian province. Both migration types have dramatically increased in China in recent decades.