Who is having the second baby? Educational assortative mating and transition to the second child in China

China continues to experience low fertility despite the lifting of the One-Child Policy in 2015. Most explanations focus on limited resources and ignore the role of educational assortative mating and couple dynamics. We use data from China Family Panel Study to address the link between educational pairing and progression to the first and second births. Using the diagonal reference model (DRM) and event-history analysis, we found different associations between educational pairings and fertility outcomes across birth orders. For the first birth, educational hypogamous couples (W > H) present the lowest progression likelihood. For the second birth, although it does not have a significant association with educational assortative mating status alone, couples’ fertility intention mismatch moderates the relationships between educational assortative mating and second childbirth. Specifically, when only the husband wants a second child, educational hypogamous couples are significantly less likely to have a second child than educational homogamous and hypergamous (W < H) couples. This research sheds light on the mechanisms between educational assortative mating, couple dynamics, and fertility outcomes.