title: Absence of an environmental effect on the recurrence of facial-cleft defects.
abstract: BACKGROUND
  The rate of recurrence of a broad range of birth defects may decrease among women who change residence after the birth of their first infant. The aim of the present study was to determine the effect of changing residence on the recurrence of congenital facial-cleft defects.
  
  
  METHODS
  We identified 4189 women who had infants with facial-cleft defects by linking a data base comprising the records of children with facial clefts born between 1952 and 1987 with the Central Person Registry in Denmark. Among the 4189 mothers, 1902 each had additional children after the first child with a facial-cleft defect. A total of 2692 younger siblings were identified. We compared the proportion of infants with facial-cleft defects among the younger siblings between mothers who had changed municipalities or sexual partners and those who had not.
  
  
  RESULTS
  Changing the municipality of residence did not decrease the frequency with which facial-cleft defects recurred in younger siblings. Among the 907 infants of mothers who changed municipalities but not partners, 29 (3.2 percent) had facial-cleft defects, as compared with 48 (3.4 percent) of 1425 infants of mothers who changed neither municipality nor partner (relative risk, 0.9; 95 percent confidence interval, 0.6 to 1.5). However, a change of partner reduced the recurrence risk significantly. Among 236 infants of mothers who changed partners, 1 (0.4 percent) had a facial-cleft defect, as compared with 77 (3.3 percent) of 2350 infants of mothers who did not change partners (relative risk, 0.1; 95 percent confidence interval, 0.02 to 0.9).
  
  
  CONCLUSIONS
  Recurrence of facial-cleft defects is not linked to the residence of the mother, but having a different partner reduced a woman's risk of having a second child with this defect.
authors.affiliation: Danish Epidemiology Science Center research unit, Steno Institute of Public Health, Aarhus.
authors.forename: K
authors.initials: K
authors.lastname: Christensen
authors.forename: M M
authors.initials: MM
authors.lastname: Schmidt
authors.forename: M
authors.initials: M
authors.lastname: Vaeth
authors.forename: J
authors.initials: J
authors.lastname: Olsen
mesh_terms: D002971:Cleft Lip / Q000453:epidemiology / Q000209:etiology* / Q000235:genetics; D002972:Cleft Palate / Q000453:epidemiology / Q000209:etiology* / Q000235:genetics; D003718:Denmark / Q000453:epidemiology; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D010334:Paternity; D012042:Registries; D012307:Risk Factors