title: Thymus size and head circumference at birth and the development of allergic diseases.
abstract: BACKGROUND
  The positive association between a large head circumference at birth and total serum IgE levels has been suggested to be due to negative associations between head circumference at birth and thymus development and between thymus development and total serum IgE levels.
  
  
  OBJECTIVE
  To examine the associations between head circumference and thymus size at birth and the development of allergic disease.
  
  
  METHODS
  The size of the thymus was assessed by sonography during the first week of life in 149 healthy term infants. Information on birth characteristics and mode of delivery was collected at delivery. The presence of allergic disease was assessed 5 years later by mailed questionnaires, which were returned by 85% of the eligible families.
  
  
  RESULTS
  At birth, head circumference was positively associated with thymus size (P < 0.001). In all, 27 (23%) of the children had developed at least one allergic disease. Multivariate analysis revealed that both parental allergy (Prevalence Ratio and 95% CI) = 3.18 (1.49-6.78)) and caesarean delivery (2.62 (1.48-4.64)) were independently correlated with allergic disease, whereas thymus size was not.
  
  
  CONCLUSIONS
  Our study does not support that a large head circumference is associated with a small thymus size, nor that a small thymus size is associated with allergic disease. Whether thymus size at birth is related to total serum IgE levels still remains to be elucidated.
authors.affiliation: Department of Epidemiology Research, Danish Epidemiology Science Centre, Statens Serum Institut, Coenhagen, Denmark. cb@ssi.dk
authors.forename: C S
authors.initials: CS
authors.lastname: Benn
authors.forename: D L
authors.initials: DL
authors.lastname: Jeppesen
authors.forename: H
authors.initials: H
authors.lastname: Hasselbalch
authors.forename: A B
authors.initials: AB
authors.lastname: Olesen
authors.forename: J
authors.initials: J
authors.lastname: Nielsen
authors.forename: B
authors.initials: B
authors.lastname: Björkstén
authors.forename: I
authors.initials: I
authors.lastname: Lisse
authors.forename: P
authors.initials: P
authors.lastname: Aaby
mesh_terms: D001724:Birth Weight / Q000502:physiology*; D001827:Body Height / Q000502:physiology; D002585:Cesarean Section; D005314:Embryonic and Fetal Development / Q000276:immunology*; D005260:Female; D005500:Follow-Up Studies; D006257:Head / Q000098:blood supply / Q000254:growth & development*; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology; D007073:Immunoglobulin E / Q000097:blood; D007229:Infant Welfare; D007231:Infant, Newborn; D008297:Male; D015999:Multivariate Analysis; D011446:Prospective Studies; D012016:Reference Values; D012307:Risk Factors; D011795:Surveys and Questionnaires; D013950:Thymus Gland / Q000098:blood supply / Q000254:growth & development*
chemical_list: D007073:Immunoglobulin E