title: Geographic variations in probability of pregnancy in four cities of France.
abstract: BACKGROUND
  Several studies have described geographic variations in human fecundability, but this phenomenon has almost exclusively been studied at an international level rather than within a given country. Our aim was to describe geographic variations in fecundability, the monthly probability of pregnancy, between four cities of France.
  
  
  METHODS
  We conducted a cross-sectional study in four French maternity units from Toulouse, Rennes, Lyons and Paris, among partners of pregnant women. Women were asked about the time to pregnancy (TTP) of their current pregnancy. TTP was analysed with a discrete Cox model allowing to estimate fecundability ratios (FR).
  
  
  RESULTS
  Time to pregnancy was defined for 894 couples. There was no strong evidence of heterogeneity in fecundability between the four compared cities (p=0.05 without adjustment and p=0.25 after adjustment for behavioural and medical factors). The highest fecundability was observed in Rennes and the lowest in Toulouse (fecundability ratio (FR)=1.28, 95% CI: 1.01-1.63). Differences in fecundability were smaller between the other cities.
  
  
  CONCLUSIONS
  We highlighted a possibly slightly higher fecundability in Rennes compared to Toulouse. Possible explanations for this finding are discussed. We note that the finding is consistent with previous observations indicating a higher sperm concentration among semen donors in Rennes than in Toulouse.
authors.affiliation: INSERM (National Institute For Health and Medical Research) U569, IFR 69, 82, rue Général-Leclerc, 94276 Le Kremlin-Bicêtre Cedex, France. muller@vjf.inserm.fr
authors.forename: A
authors.initials: A
authors.lastname: Muller
authors.forename: R
authors.initials: R
authors.lastname: Slama
authors.forename: C
authors.initials: C
authors.lastname: Labbé-Declèves
authors.forename: P
authors.initials: P
authors.lastname: Jouannet
authors.forename: L
authors.initials: L
authors.lastname: Bujan
authors.forename: R
authors.initials: R
authors.lastname: Mieusset
authors.forename: D
authors.initials: D
authors.lastname: Le Lannou
authors.forename: J-F
authors.initials: JF
authors.lastname: Guerin
authors.forename: M
authors.initials: M
authors.lastname: Benchaib
authors.forename: A
authors.initials: A
authors.lastname: Spira
mesh_terms: D003430:Cross-Sectional Studies; D005260:Female; D005298:Fertility; D005602:France / Q000453:epidemiology; D006801:Humans; D008297:Male; D011247:Pregnancy; D013997:Time Factors