Morphological factors influencing the penetration of human sperm into cervical mucus in vitro.

The efficiency of cervical mucus in filtering out single, multiple and associated abnormalities of human spermatozoa was determined. Twenty semen samples which gave a normal in vitro cervical mucus penetration test (CMPT) were analysed before and after migration using a detailed classification system (13 categories). The % of normal forms was significantly increased in cervical mucus (59.5 vs 33.2%), whereas the % of sperm with single, multiple or associated abnormalities of the midpiece or of the flagellum were found to decrease significantly in cervical mucus. Sperm with single or multiple abnormalities confined to the head migrated similarly to normal forms. The decrease in amorphous and elongated tapering sperm was explained by their more frequent association with other defects of the midpiece and/or of the flagellum.