title: Is there evidence for aetiologically distinct subgroups of idiopathic congenital talipes equinovarus? A case-only study and pedigree analysis.
abstract: BACKGROUND
  Idiopathic congenital talipes equinovarus (CTEV) is a common developmental foot disorder, the aetiology of which remains largely unknown. Some aspects of the epidemiology suggest the possibility of aetiologically distinct subgroups. Previous studies consider CTEV as a homogenous entity which may conceal risk factors in particular subgroups. We investigate evidence for aetiologically distinct subgroups of CTEV.
  
  
  METHODS
  Parents of 785 probands completed a postal questionnaire. Family pedigrees were compiled by telephone. Case-only analysis was used to investigate interactions between risk factors and sex of the proband, CTEV laterality and CTEV family history.
  
  
  RESULTS
  The male:female ratio was 2.3:1, 58% of probands were affected bilaterally and 11% had a first-second degree family history. There were modest interactions between family history and twin births (multivariate case - only odds ratio [ORca] = 3.87, 95%CI 1.19-12.62) and family history and maternal use of folic acid supplements in early pregnancy (ORca = 0.62, 95%CI 0.38-1.01); and between sex of the proband and maternal alcohol consumption during pregnancy (female, positive history and alcohol consumed: ORca = 0.33, 95%CI 0.12-0.89). Previous reports of an interaction between maternal smoking and family history were not confirmed. Relatives of female probands were affected more often than relatives of male probands.
  
  
  CONCLUSIONS
  These results provide tentative evidence for aetiologically distinct CTEV subgroups. They support the 'Carter effect', suggesting CTEV develops though a multifactorial threshold model with females requiring a higher risk factor 'load', and suggest areas where future aetiological investigation might focus. Large multi-centre studies are needed to further advance understanding of this common condition.
authors.affiliation: Clubfoot Research Group, University of Aberdeen, Aberdeen, Scotland. a.h.cardy@abdn.ac.uk
authors.forename: Amanda H
authors.initials: AH
authors.lastname: Cardy
authors.forename: Linda
authors.initials: L
authors.lastname: Sharp
authors.forename: Nicola
authors.initials: N
authors.lastname: Torrance
authors.forename: Raoul C
authors.initials: RC
authors.lastname: Hennekam
authors.forename: Zosia
authors.initials: Z
authors.lastname: Miedzybrodzka
mesh_terms: D000328:Adult; D003025:Clubfoot / Q000209:etiology* / Q000235:genetics; D005260:Female; D006801:Humans; D008297:Male; D008423:Maternal Age; D010331:Paternal Age; D010375:Pedigree; D011795:Surveys and Questionnaires