Male factors and the likelihood of pregnancy in infertile couples. I. Study of sperm characteristics.

A prospective study of 394 infertile men was conducted over 3 years following a primary semen analysis. The cumulative pregnancy rate was 43 and 64% after 1 and 3 years, respectively. The pregnancy rate was significantly higher in the secondary infertile group. The study of various sperm factors and the occurrence of pregnancy showed that they were not of equal significance in predicting male fertility potential. The percentage of pregnancies decreased significantly only when the sperm concentration was less than 5 x 10(6)/ml. The pregnancy rate increased significantly with the percentage of motile sperm. The percentage of sperm with normal morphology was also found to be significantly higher when a pregnancy occurred than when the couple remained infertile (43.6% vs 37.7%). In a detailed morphological analysis of the sperm, six abnormalities (microcephaly, double head, amorphous head, cytoplasmic droplet, bent tail and coiled tail) were found to be significantly more frequent when a pregnancy did not occur. The most predictive value was given by the Multiple Anomalies Index (MAI), which is the mean number of abnormalities observed per abnormal sperm. The pregnancy rate was significantly lower after both 1 and 3 years when the MAI was greater than 1.6. Multivariate analysis showed that the best prognostic indicator of fertility was given by the percentage of motile sperm and the MAI, particularly in patients with primary infertility.