Mom's Dust Mite Exposure Shared with Her Fetus

NEW YORK (Reuters Health) - Asthma and allergy researchers have found dust mite allergens in umbilical cord blood of some infants whose mothers were positive for the allergen, whereas none of the newborns whose mothers were negative for the common dust mite allergen known as Der p 1 carried the allergen themselves.

Early life exposure to dust mite allergen has been linked to childhood asthma risk. The finding that in utero exposure occurs as well suggests mothers could reduce their children's asthma risk by limiting their own allergen exposure, Dr. Abdul Bahrainwala of Wayne State University in Detroit and colleagues note in the Annals of Allergy, Asthma & Immunology.

Risk of asthma and allergy is much higher in children whose mothers have the conditions than in those whose fathers do, suggesting there may be a maternal effect that goes beyond gene transmission, the researchers note.

A past study found Der p 1 in the fetus-cushioning amniotic fluid and umbilical cord blood of some fetuses whose mothers had high levels of allergens in their homes. It remains unclear why the allergens were found in some but not all of the infants, and how the transmission might occur.

To investigate the relationship further, the researchers measured levels of Der p 1 in 98 mothers and their newborns. Twenty-seven (28 percent) of the women tested positive for the allergen, while 12 of the infants had detectable levels of the allergen in their cord blood.

Data analysis revealed a direct correlation between maternal allergen and newborn allergen levels in 12 newborns and their mothers. Levels in infants were roughly one third of those found in the mothers.

These findings suggest that in addition to childhood avoidance of allergens, prevention or avoidance of maternal allergen exposure during pregnancy might further reduce the prevalence of childhood asthma, the researchers conclude.

SOURCE: Annals of Allergy, Asthma and Immunology, November 2005.