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.