title: Twin pregnancy possibly associated with high semen quality.
abstract: BACKGROUND
  Recent studies found an association between a long waiting time to pregnancy (TTP) and reduced probability of twinning and a reduced dizygotic (DZ) twinning rate in subfertile men. However, it remains unsolved whether semen quality is associated with twin offspring. We therefore studied the semen quality in a group of fathers of naturally conceived twins.
  
  
  METHODS
  In this study, 37 fathers of DZ twins and 15 fathers of monozygotic (MZ) twins participated, and 349 normal fertile men served as a reference group. All men delivered a semen sample, underwent a physical examination and completed a questionnaire.
  
  
  RESULTS
  After adjustment, fathers of DZ and MZ twins had 3.6 (95% CI 1.7; 5.4) and 4.6 (95% CI 2.0; 7.2) percentage points higher percentage of sperm cells with normal morphologic features and percentages of motile sperm cells were 11.5 (95% CI 7.2; 15.9) and 12.5 (95% CI 6.3; 18.6) percentage points higher than the reference group (P < 0.01). Fathers of DZ twins and MZ twins had 24.7 (95% CI; -9.1; 71.3) and 17.0% (-25.2%; 83.0%) higher sperm concentration than the reference group.
  
  
  CONCLUSIONS
  Fathers of DZ twins had a better semen quality than the reference group, which supports the assumption that spontaneous DZ twinning rate can be used as a sensor of male fecundity of a population.
authors.affiliation: University Department of Growth and Reproduction, University Hospital of Copenhagen, Denmark. camilla.asklund@rh.hosp.dk
authors.forename: Camilla
authors.initials: C
authors.lastname: Asklund
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: Tabor
authors.forename: L
authors.initials: L
authors.lastname: Sperling
authors.forename: N E
authors.initials: NE
authors.lastname: Skakkebaek
mesh_terms: D005260:Female; D005298:Fertility; D006801:Humans; D008297:Male; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000502:physiology*; D012661:Semen / Q000502:physiology*; D013076:Sperm Count; D013081:Sperm Motility; D014427:Twins; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic