Human sperm morphology and the outcome of modified Kremer tests.

The outcome of homologous in vitro tests of human sperm penetration into cervical mucus in couples undergoing infertility investigations have been shown to be correlated with the proportion of morphologically normal spermatozoa in the semen samples used for the tests. In addition, the ejaculates producing poor tests contained significantly more spermatozoa with defective tails than those semen samples producing normal or, surprisingly, negative tests.