This test evaluates whether a man's sperm can travel through cervical mucus. It is one of the test done to determine the cause of infertility and whether it is related to a problem with the man's sperm or a woman's mucous. During the woman's ovulation, samples of her cervical mucus and the man's semen are collected for this test. In the lab, the semen is added to the mucus in a tube. After sometime, the distance that the sperm have traveled is measured.

The mucus penetration test is also done (a) with a donor sperm and the woman's mucus or (b) with donor mucus and the man's sperm, to see whether the problem is with the woman's mucus or the man's sperm.

If both the man's sperm and the donor sperm do not penetrate the woman's mucous, the problem is likely to be with the woman's mucous. If the man's sperm do not penetrate while the donor sperm can penetrate a woman's mucous the problem is likely to be with the man's sperm.