RESUMO
OBJECTIVE: To evaluate the associations between the results of the male partner's semen analysis (classified according to the World Health Organization [WHO] criteria) and fathering a child without any treatment. DESIGN: Prospective multicenter cohort study. SETTING: Twenty subfertility centers in The Netherlands. PATIENT(S): A total of 3,345 consecutive couples presenting for subfertility. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Associations between the results of the male partner's semen analysis, classified according to the WHO criteria, and fathering a child without any treatment within a time horizon of 1 year. Subsequently, we redefined semen quality criteria and reevaluated the associations. RESULT(S): Follow-up data of 3,129 couples (94%) were available, of which 517 (17%) had a healthy pregnancy without treatment. The 1-year pregnancy rate in men with WHO normozoospermia did not differ significantly from that in men with WHO impaired semen (24% vs. 23%). In contrast, we observed lower chances of fathering a child for sperm concentrations <40 × 10(6)/mL, total sperm count <200 × 10(6), and sperm morphology <20% normal forms. With a multivariable regression model based on the redefined male semen subfertility criteria we were able to make a finer differentiation between subfertile men, with probabilities of fathering a child ranging from 7% to 41%. CONCLUSION(S): The current WHO criteria for semen quality do not discriminate between fertile and subfertile men. Our redefined and graded semen criteria have strong predictive value. If interpreted correctly, the fast and inexpensive semen analysis remains the gold standard for defining a man's role in subfertility.