We assessed whether prenatal selenium (Se) exposure is associated with anthropometry at birth, placental weight and gestational age. Study subjects were 1249 mother-child pairs from the Valencia and Gipuzkoa cohorts of the Spanish Childhood and Environment Project (INMA, 2003–2008). Se was determined in serum samples taken at the first trimester of pregnancy.
Socio-demographic and dietary characteristics were also collected by questionnaires. Mean (SD) serum Se concentration was 79.57 (9.64) μg/L. Se showed weak associations with both head circumference and gestational age. The association between serum Se concentration and birth weight and length was negative, and direct for placental weight and probability of preterm birth,
although the coefficients did not reach statistical significance. Individuals with total mercury (THg) levels >15 μg/L reversed the serum Se concentration effect on head circumference. Significant interactions were found between sex and both gestational age and prematurity. Spontaneous birth gestational ages were estimated to be lower for males and their probability of prematurity was higher. In conclusion, prenatal Se exposure may be associated with lower head circumference and lower gestational ages at spontaneous birth. Interactions with THg exposure and gender should be considered when assessing these relationships.