Detection of house-dust-mite allergen in amniotic fluid and umbilical-cord blood

Mononuclear cells In umbilical-cord blood display allergen-specific reactivity, but how allergen exposure occurs In utero is unknown. We Investigated the presence of a common inhalant allergen (Der p 1), to which mothers are exposed throughout pregnancy, by ELISA in matched maternal blood and amniotic fluid samples at 16-17 weeks of gestation, and in matched maternal and umbilical-cord blood at term (greater than or equal to 37 weeks of gestation). Der p 1 was detectable In 24 of 43 amniotic fluid samples where It was also present In maternal blood, and in 15 of 24 cord-plasma samples at significantly higher concentrations than in the maternal plasma (p=0.022). The detection of Der p 1 In the amniotic fluid and the fetal circulation provides direct evidence of transamniotic and transplacental allergen exposure.