Disgust in pregnancy and fetus sex--longitudinal study.

Disgust, an emotion triggering behavioral avoidance of pathogens, serves as a first line of defense against infections. Since behavior related to disgust involves some cost, the aversive reaction should be adjusted to the level of an individual's immunocompetence, and raise only when immunological function is lower (e.g. during pregnancy). We studied changes in disgust sensitivity in pregnant women, and tested if disgust sensitivity is related to a fetus's sex. 92 women participated in a three-stage research, answering the Disgust Scale-Revised questionnaire at each trimester of pregnancy. The result showed that total disgust and disgust sensitivity in the Core Domain were the highest in the first trimester (when maternal immunosuppression is also the highest), and decreased during pregnancy in women bearing daughters. Women bearing sons had relatively high disgust sensitivity persisting in the first and in the second trimester. The elevation in disgust sensitivity during the second trimester for mothers bearing male fetus can be explained by the necessity to protect for a longer time, a more ecologically sensitive fetus, and also herself when bearing a more energetically costly sex. The proximate mechanism may involve the differences in maternal testosterone and cortisol concentrations in the second trimester of pregnancy.