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Normally, mucus in the cervix (the lower part of the uterus that opens into the vagina) is thick and impenetrable to sperm until just before release of an egg (ovulation). Then, just before ovulation, the mucus becomes clear and elastic (because the level of the hormone estrogen increases). As a result, sperm can move through the mucus into the uterus to the fallopian tubes, where fertilization can take place. If the mucus does not change at ovulation (usually because of an infection), pregnancy is unlikely. Pregnancy is also unlikely if the mucus contains antibodies to sperm, which kill sperm before they can reach the egg.
Diagnosis and
Treatment
A postcoital test, performed between 2 and 8 hours after sexual intercourse, involves evaluating cervical mucus and determining whether sperm can survive in the mucus. The test is scheduled for the midpoint of the menstrual cycle, when the estrogen level is highest and the woman is ovulating. A sample of mucus is taken with forceps or a syringe. The thickness and elasticity of the mucus and the number of sperm in the mucus are determined. Abnormal results include overly thick mucus, no sperm, and sperm clumping together because the mucus contains antibodies to the sperm. However, abnormal results do not always indicate that there is a problem with the mucus or that pregnancy cannot occur. Sperm may be absent only because they were not deposited into the vagina during intercourse, and the mucus may be overly thick only because the test was not performed at the proper time in the menstrual cycle.
Treatment may include intrauterine insemination, in which semen is placed directly in the uterus to bypass the mucus. Drugs to thin the mucus, such as guaifenesin, may be used. However, there is no proof that either treatment increases the chances of pregnancy.
Last full review/revision February 2003
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