The diagnosis of male infertility--prospective time-specific study of conception rates related to seminal analysis and post-coital sperm-mucus penetration and survival in otherwise unexplained infertility.

Infertile women without any inherent female infertility factors and able to secrete normal cervical mucus were studied prospectively in relation to post-coital sperm-mucus penetration (PCT) and their partner's seminal analysis, excluding men with azoospermia. Time-specific cumulative conception rates calculated as for life-table analysis were related to each measured seminal variable on routine analysis of 2-3 samples (volume, density, proportion with progressive motility, and proportion with normal morphology); to various derivatives from combinations of these variables; to seminal findings after vital staining; and to the PCT results. The best seminal predictor of fertility was the motile normal sperm density (MNSD), the 18 month conception rates being 57.4% +/- 4.6 (SE) and 30.2% +/- 5.9 (ratio 1.9, P less than 0.001) above and below a derived threshold value of 4 x 10(6)/ml. The PCT led to rates of 55.6% +/- 4.3 and 14.9% +/- 5.1 (ratio 3.73, P less than 0.001) for positive and negative results, respectively. The PCT also gave rise to a significantly distinct intermediate poor-positive sub-group (conception rate 30.6% +/- 9.0). Seminal analysis (the MNSD) did not affect the conception rate associated with a positive PCT but helped to discriminate further with a negative PCT (conception rates 22.5% +/- 8.7 with an MNSD above 4 x 10(6)/ml versus 5.6% +/- 4.8 below, P less than 0.05). The PCT was the single best predictor of fertility but seminal analysis (the MNSD) was of additional value after a negative PCT.