LAUSR

Summary Many factors influence the male:female birth ratio (number of male births divided by total births, M/T). Studies have suggested that this ratio may be positively correlated with the education levels of mothers. This study assessed the effect of maternal education on M/T in the US population overall and by racial group. Number of live births by sex of the child, maternal educational level reached and race were obtained from the Centres for Disease Control (CDC Wonder) for the period 2007–2015. The total study sample comprised 28,268,183 live births. Overall, for the four available recorded racial groups (Asian/Pacific Islander, White, American Indian/Alaska Native and Black/African American), M/T rose significantly with increasing education levels (p<0.0001). When analysed by race, this relationship was only found for White births (p<0.0001). The M/T of Black births rose with increasing maternal education level up to associate degree level (p=ns), then fell significantly with higher levels of education (χ 2=4.5, p=0.03). No significant trends were present for Asian/Pacific Islander or American Indian/Alaska Native births. Socioeconomic indicators are generally indicators of better condition and in this study educational attainment was overall found to be positively correlated with M/T, supporting the Trivers–Willard hypothesis.