Key PointsQuestionWas the 2017 health insurance mandate for assisted reproduction associated with increases in multiple pregnancies and births in Korea?FindingsThis cohort study of 1 474 484 women found that the possibility of multiple pregnancies and multiple births increased significantly after coverage for assisted reproductive technology treatment. The number of total births per pregnant woman was on a decreasing trend before the intervention but began to increase after the intervention.MeaningThese findings suggest that policies that provide financial support for infertility treatment may contribute to addressing Korea’s low birth rates.