title: Time to pregnancy and semen parameters: a cross-sectional study among fertile couples from four European cities.
abstract: BACKGROUND
  In fertile populations, little is known about the association between semen parameters and time to pregnancy (TTP).
  
  
  METHODS
  Pregnant women from Copenhagen, Edinburgh, Paris and Turku who conceived without medical intervention were asked for their TTP (942 couples), and their partners provided a semen sample. The proportion of morphologically normal sperm and the multiple anomalies index (MAI, ratio of the total number of anomalies to the number of abnormal sperm) were centrally estimated. We estimated rate ratios for the occurrence of a pregnancy by a discrete survival model, adjusted for sexual activity and female factors affecting fecundity.
  
  
  RESULTS
  Increasing sperm concentration influenced TTP up to 55 x 10(6)/ml. The proportion of morphologically normal sperm influenced TTP up to 39% according to David's criteria, and this association held among the subjects with a sperm concentration >55 x 10(6)/ml. For strict criteria, the threshold value was 19% normal sperm. An increase of 0.5 in MAI was associated with an adjusted rate ratio for the occurrence of a pregnancy of 0.68 (95% confidence interval: 0.54-0.85).
  
  
  CONCLUSIONS
  These results highlight the importance of sperm morphology parameters and indicate that the effect of proportion of normal sperm on TTP may be independent of sperm concentration.
authors.affiliation: INSERM U292, Research in Public Health, 82 rue du Général Leclerc, 94276 Le Kremlin-Bicêtre cedex, France. slama@vjf.inserm.fr
authors.forename: R
authors.initials: R
authors.lastname: Slama
authors.forename: F
authors.initials: F
authors.lastname: Eustache
authors.forename: B
authors.initials: B
authors.lastname: Ducot
authors.forename: T K
authors.initials: TK
authors.lastname: Jensen
authors.forename: N
authors.initials: N
authors.lastname: Jørgensen
authors.forename: A
authors.initials: A
authors.lastname: Horte
authors.forename: S
authors.initials: S
authors.lastname: Irvine
authors.forename: J
authors.initials: J
authors.lastname: Suominen
authors.forename: A G
authors.initials: AG
authors.lastname: Andersen
authors.forename: J
authors.initials: J
authors.lastname: Auger
authors.forename: M
authors.initials: M
authors.lastname: Vierula
authors.forename: J
authors.initials: J
authors.lastname: Toppari
authors.forename: A N
authors.initials: AN
authors.lastname: Andersen
authors.forename: N
authors.initials: N
authors.lastname: Keiding
authors.forename: N E
authors.initials: NE
authors.lastname: Skakkebaek
authors.forename: A
authors.initials: A
authors.lastname: Spira
authors.forename: P
authors.initials: P
authors.lastname: Jouannet
mesh_terms: D003430:Cross-Sectional Studies; D005060:Europe; D005260:Female; D005298:Fertility; D005306:Fertilization; D006801:Humans; D008297:Male; D011247:Pregnancy; D011336:Probability; D012661:Semen / Q000502:physiology*; D013076:Sperm Count; D013094:Spermatozoa / Q000166:cytology; D013997:Time Factors