We study the determinants of season of birth for married women aged 20-45 in the USA, using birth certificate and Census data. We also elicit the willingness to pay for season of birth through discrete-choice experiments implemented on the Amazon Mechanical Turk platform. We document that the probability of a spring first birth is significantly related to mother's age, education, race, ethnicity, smoking status during pregnancy, receiving WIC (Women, Infants & Children) food benefits during pregnancy, prepregnancy obesity, and the mother working in education, training, and library occupations; whereas among unmarried women without a father acknowledged on their child's birth certificate, all our findings are muted. A summer first birth does not depend on socioeconomic characteristics, although it is the most common birth season in the USA. Among married women aged 20-45, we estimate the average marginal willingness to pay (WTP) for a spring birth to be 877 USD. This implies a willingness to trade-off 560 grams of birth weight in the normal range to achieve a spring birth. Finally, we estimate that an increase of 1,000 USD in the predicted marginal WTP for a spring birth is associated with a 15 pp (percentage points) increase in the probability of obtaining an actual spring birth.
