Automated semen analysis: 'zona pellucida preferred' sperm morphometry and straight-line velocity are related to pregnancy rate in subfertile couples.

BACKGROUND Standard semen analysis has low objectivity and reproducibility and is not closely related to fertility. We assess the prognostic value of automated measurements of sperm motility and morphology. METHODS During 1997-1999, 1191 infertile couples with no known absolute barrier to conception were assessed by conventional semen analysis, and automated measurements of average straight-line velocity (VSL) and the percentage of sperm with characteristics that conform to those of sperm which bind to the zona pellucida of the human oocyte (%Z). During follow-up to 2001, there were 336 natural pregnancies. RESULTS Only %Z, VSL and female age were independently significantly related to pregnancy rate by Cox regression analysis. Pregnancy rate was higher with above average %Z and VSL, indicating a continuous rather than a threshold relationship. The likelihood of pregnancy within 12 cycles can be evaluated for specific values of %Z, VSL and female age using the Cox regression model. CONCLUSIONS The automated semen measures of sperm morphometry (%Z) and velocity (VSL) are related to pregnancy rates in subfertile couples and should assist clinicians in counselling subfertile patients about their prognosis for a natural pregnancy. Objective automated methods should replace the traditional manual assessments of semen quality.