This study explored how social pressure related to parental preference for the sex of their children affects fertility. Pre-war and post-war generations were compared using individual level data previously collected in Japan in 2002. In the pre-war generation, if the first child was a daughter, the total number of children tended to increase not only when the mother preferred a son, but also when the mother did not have a preference for either gender. This tendency was not observed for the post-war generation. Results suggest that social pressure related to giving birth to a son led to high fertility in the pre-war generation; however, fertility was not influenced by social pressure in the post-war generation.