title: Exposure to high doses of birch pollen during pregnancy, and risk of sensitization and atopic disease in the child.
abstract: BACKGROUND
  The role of maternal allergen exposure during pregnancy in sensitization and development of atopic disease in the child remains controversial. In the spring of 1993, extremely high levels of birch pollen were recorded in Stockholm, Sweden. In 1994, the corresponding pollen levels were low. The aim of this study was to assess the influence of exposure during pregnancy to high/low doses of birch pollen on the risk of sensitization and development of atopic disease in children. In addition, a comparison was made with children exposed to birch pollen in early infancy.
  
  
  METHODS
  Three hundred and eighty-seven children with atopic heredity, born in Stockholm in July-October 1993 or 1994 (mothers exposed during pregnancy), were investigated at age 4.5 years. The children were clinically examined and were skin prick tested (SPT) with inhalant and food allergens. IgE antibodies (RAST) against birch pollen and recombinant birch pollen allergen (rBet v 1) were analysed in serum. A comparison was made with a similar group of children exposed during the same incident, but in the first 3 months of life, in 1993.
  
  
  RESULTS
  The children of mothers high-dose exposed during pregnancy in 1993 tended to be more sensitized (SPT > or = 3 mm) to birch pollen than the children with low-dose exposure during the corresponding period in 1994 (7.6 and 4.6%, respectively, OR: 1.7; 95% CI: 0.7-4.1). A similar but weak tendency was seen for positive RAST analyses (> or =0.35 kU/l) against birch pollen and rBet v 1. Children of mothers high-dose exposed during pregnancy were significantly less sensitized to birch pollen than the children high-dose exposed in early infancy (17.9%, OR: 0.4; 95% CI: 0.2-0.7). There was an overall trend towards a slightly increased prevalence of bronchial asthma, allergic rhinoconjunctivitis and atopic dermatitis in the group with mothers high-dose exposed during pregnancy, compared to those with low exposure.
  
  
  CONCLUSIONS
  Exposure of the mother during pregnancy to high levels of birch pollen resulted in a tendency towards increased risk of sensitization to the same allergen and symptoms of atopic disease in children with atopic heredity. Furthermore, our data indicate that exposure of the mother during pregnancy to inhalant allergens is less likely to result in sensitization in the child than exposure of the child in early infancy.
authors.affiliation: Department of Paediatrics B57, Huddinge University Hospital, S-14186 Stockholm, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Kihlström
authors.forename: G
authors.initials: G
authors.lastname: Lilja
authors.forename: G
authors.initials: G
authors.lastname: Pershagen
authors.forename: G
authors.initials: G
authors.lastname: Hedlin
mesh_terms: D001249:Asthma / Q000453:epidemiology; D002675:Child, Preschool; D003233:Conjunctivitis, Allergic / Q000453:epidemiology; D003876:Dermatitis, Atopic / Q000453:epidemiology; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D006967:Hypersensitivity / Q000150:complications / Q000175:diagnosis / Q000209:etiology*; D007231:Infant, Newborn; D011058:Pollen / Q000276:immunology*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D015995:Prevalence; D011852:Radioallergosorbent Test; D012220:Rhinitis / Q000453:epidemiology / Q000209:etiology; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology; D014197:Trees / Q000276:immunology*