title: Difference in prevalence of congenital cryptorchidism in infants between two Nordic countries.
abstract: BACKGROUND
  Several investigators have shown striking differences in semen quality and testicular cancer rate between Denmark and Finland. Since maldescent of the testis is a shared risk factor for these conditions we undertook a joint prospective study for the prevalence of congenital cryptorchidism.
  
  
  METHODS
  1068 Danish (1997-2001) and 1494 Finnish boys (1997-99) were consecutively recruited prenatally. We also established prevalence data for all newborns at Turku University Central Hospital, Finland (1997-99, n=5798). Testicular position was assessed by a standardised technique. All subtypes of congenital cryptorchidism were included, but retractile testes were considered normal.
  
  
  RESULTS
  Prevalence of cryptorchidism at birth was 9.0% (95% CI 7.3-10.8) in Denmark and 2.4% (1.7-3.3) in Finland. At 3 months of age, prevalence rates were 1.9% (1.2-3.0) and 1.0% (0.5-1.7), respectively. Significant geographic differences were still present after adjustment for confounding factors (birthweight, gestational age, being small for gestational age, maternal age, parity, mode of delivery); odds ratio (Denmark vs Finland) was 4.4 (2.9-6.7, p<0.0001) at birth and 2.2 (1.0-4.5, p=0.039) at three months. The rate in Denmark was significantly higher than that reported 40 years ago.
  
  
  CONCLUSIONS
  Our findings of increasing and much higher prevalence of congenital cryptorchidism in Denmark than in Finland contribute evidence to the pattern of high frequency of reproductive problems such as testicular cancer and impaired semen quality in Danish men. Although genetic factors could account for the geographic difference, the increase in reproductive health problems in Denmark is more likely explained by environmental factors, including endocrine disrupters and lifestyle.
authors.affiliation: University Department of Growth and Reproduction, Rigshospitalet DK-2100 Copenhagen, Denmark.
authors.forename: K A
authors.initials: KA
authors.lastname: Boisen
authors.forename: M
authors.initials: M
authors.lastname: Kaleva
authors.forename: K M
authors.initials: KM
authors.lastname: Main
authors.forename: H E
authors.initials: HE
authors.lastname: Virtanen
authors.forename: A-M
authors.initials: AM
authors.lastname: Haavisto
authors.forename: I M
authors.initials: IM
authors.lastname: Schmidt
authors.forename: M
authors.initials: M
authors.lastname: Chellakooty
authors.forename: I N
authors.initials: IN
authors.lastname: Damgaard
authors.forename: C
authors.initials: C
authors.lastname: Mau
authors.forename: M
authors.initials: M
authors.lastname: Reunanen
authors.forename: N E
authors.initials: NE
authors.lastname: Skakkebaek
authors.forename: J
authors.initials: J
authors.lastname: Toppari
mesh_terms: D001724:Birth Weight; D003456:Cryptorchidism / Q000145:classification / Q000150:complications / Q000453:epidemiology*; D003718:Denmark / Q000453:epidemiology; D005387:Finland / Q000453:epidemiology; D005865:Gestational Age; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature; D007236:Infant, Small for Gestational Age; D008297:Male; D015995:Prevalence; D013736:Testicular Neoplasms / Q000453:epidemiology / Q000209:etiology