Previous studies have revealed that advanced maternal age is a major risk factor for various adverse obstetric and perinatal outcomes [4–6, 21, 22]. Indeed, we observed higher rates of preterm births and low birthweight among older mothers in LSB21. Our previous study, as well as other studies, has shown that preterm birth is a risk factor for unfavorable health outcomes during subsequent years [12, 23]. However, from a socioeconomic perspective, advanced maternal age may also exert a positive impact on children’s health. Japanese women are no exception to the worldwide pattern in which delayed childbearing is associated with higher educational attainment and career investment . In LSB21, women of advanced maternal age tended to have higher educational attainment and higher family income. Evidence suggests that higher socioeconomic status (e.g., higher income and educational attainment) is beneficial for child health [25, 26]. Consequently, social advantage associated with older maternal age may compensate for biological disadvantage . Conversely, when socioeconomic disadvantage threatens maternal “fitness”, there may be an advantage to commencing childbearing at an earlier age—the so-called “weathering hypothesis” proposed by Geronimus .