Disgust in pregnancy and fetus sex—Longitudinal study Agnieszka Żelaźniewicz ⁎, Bogusław Pawłowski Department of Human Biology, University of Wroclaw, Poland HIGHLIGHTS • Disgust is a first line defense from pathogens. • Women's disgust sensitivity is heightened in the 1st trimester of pregnancy. • Changes in disgust sensitivity during pregnancy are related to the sex of a fetus. • Women carrying a son show higher disgust sensitivity in the 1st & 2nd trimester. abstract article info Article history: Received 6 May 2014 Received in revised form 8 November 2014 Accepted 10 November 2014 Available online 14 November 2014 Keywords: Disgust sensitivity Pregnancy Fetus sex Immunocompetence 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. © 2014 Elsevier Inc. All rights reserved. 1. Introduction The emotion of disgust and prophylactic behavior are parts of behav- ioral immune system, functioning as a first line of defence against infection. Disgusting stimuli triggers disease-relevant emotional and cognitive responses, facilitating pathogen avoidance [e.g. 1,2]. Although the repulsion, evoked by this emotion, provides advantages associated with the detection and avoidance of things, people, and situations that may pose some risk of infection, there are also costs involved, such as dietary selectivity, or loss of energy and time devoted to disease avoid- ance. The compensatory behavioral prophylaxis hypothesis claims, that to be adaptive, the behavioral immune system should be flexible, i.e. stronger aversive reactions should occur when the immunity is low, perceivers are more vulnerable to infection, and the cost of exposure to pathogens is high, so as to decrease the risk [2]. Previous research confirms that people, who suffer from more frequent infectious illnesses, exhibit higher disgust and contamination sensitivity [3]. Women in the luteal phase of the ovulatory cycle, when the progesterone level, and hence immunosuppression are the highest, experience increased prophylactic behavior [4]. Individual's health condition impacts even social behavior in situations involving some pathogen infection risk. For example, people who perceive themselves as more vulnerable to disease are less likely to have friends with disabil- ities [5], or exhibit stronger anti-immigrant attitudes [6]. Also, visual perception of other people's symptoms of infectious disease causes white blood cells to produce higher levels of the proinflammatory cyto- kine interleukin, after stimulation by model bacteria. It suggests that merely visual perception of symptoms of infectious disease may cause more aggressive response of the immune system [7]. In women, a very particular time of down-regulated immunological response is pregnancy. As the fetus is only in 50% genetically related to a mother, maternal immune system may attack an embryo as a foreign body. This problem is resolved through suppression of maternal immune system, potentially leaving, both mother and the fetus, more Physiology & Behavior 139 (2015) 177–181 ⁎ Corresponding author at: ul. Kuźnicza 35, 50-138 Wrocław, Poland. Tel.: +48 509345299. E-mail address: a.zelazniewicz@antropo.uni.wroc.pl (A. Żelaźniewicz). http://dx.doi.org/10.1016/j.physbeh.2014.11.032 0031-9384/© 2014 Elsevier Inc. All rights reserved. Contents lists available at ScienceDirect Physiology & Behavior journal homepage: www.elsevier.com/locate/phb