Background: Family disruption and separation form parents during childhood may have long-lasting effects on the child. Previous literature documents associations between separation from parents and cognitive ability, educational attainment, and health, but little is known about effects on subsequent reproductive behavior.

Objective: We evaluate the associations between unaccompanied evacuation to foster care and subsequent marriage and fertility behavior by comparing Finnish children who were evacuated to Swedish foster families during World War II to their non-evacuated siblings.

Methods: In total, some 49,000 children were evacuated for a period ranging from months to years. We analyze a nationally representative sample of 2,009 evacuees born in 1933-1944 by combining data collected from war time government records with 1950 and 1971 censuses and 1971-2011 population registers.

Results: Comparison of evacuated and nonevacuated same-sex siblings suggests no associations between evacuation and the probability of ever marrying, timing of first birth, and completed family size, although some associations are found in naive means comparisons. This difference in results across models is suggestive of negative selection of evacuee families.

Conclusions: We do not find consistent evidence of any causal effect of family disruption on family formation and reproductive behavior. The results are sensitive to controlling for unobserved selection and suggest that some of the adverse outcomes documented in earlier literature could change if selection was accounted for.