Understanding Medical Aspects of Infertility: the Cervix and the Uterus

These organs clearly play an enormous role in conception, so understanding their functions—and how those functions might go awry—is essential. This information will arm you with knowledge that'll be helpful if you ever undergo an infertility evaluation.

The cervix is a small neck-like structure at the base of the uterus, opening into the vagina. It normally keeps a fetus from falling out of the uterus until the end of gestation and, aided by the cervical mucus, keeps unwanted things from traveling from the vagina into the uterus.

Cervical mucus is produced by a group of cells that line the inside of the cervix known as columnar cells. The cervical mucus is really quite remarkable. During the vast majority of the cycle, it is an extremely effective barrier that prevents anything from entering into the uterus. However, for a few days just prior to ovulation, it changes dramatically. As a result of stimulation by estrogen, which is produced by the cells surrounding the maturing egg, the cervical mucus becomes very clear, almost watery, and probably actually helps rather than hinders the sperm as they try to migrate through on their way to the fallopian tubes. As soon as ovulation occurs and brings on progesterone production, the mucus again becomes thick and impenetrable.

You can track the consistency and appearance of cervical mucus yourself throughout your cycle to watch for changes around ovulation.

For a medical evaluation, the postcoital test (PCT) is a good way to evaluate not only the cervical mucus, but also the interaction of the sperm and the mucus. This test must be performed right around the time of ovulation. It cannot be performed more than a couple of days before ovulation, nor after ovulation, as the cervical mucus will be too thick for this test to be meaningful.

Following intercourse, a sample of cervical mucus is gently removed from the cervix as in a normal pelvic exam, and evaluated microscopically. The quality of the cervical mucus as well as the number of sperm present and their motility can all be checked. While it is often stated that this test must be performed within two hours of intercourse, it can actually be checked as many as 12 to 14 hours after intercourse (do not douche or take a bath, but showers are OK), as long as the physician is informed of the time. If properly timed, this test reveals a great deal about the adequacy of the cervical mucus production, the survivability of the sperm in the cervical mucus, and the interaction of the sperm and the cervical mucus.

The characteristics of the mucus that can be evaluated include:

• Ferning: When the cervical mucus dries on a microscope slide, it should take on the appearance of ferns. This assures that the mucus has been exposed to adequate levels of estrogen without any exposure to progesterone; in other words, that the timing is correct.
• Amount: Cervical mucus production normally increases dramatically just prior to ovulation.
• Clarity: It should be very clear, almost watery.
• Cellularity: There should be relatively few cells present, other than sperm.
• Spinnbarkeit: This is the stretchiness of the cervical mucus. It should be almost elastic and may stretch ten centimeters or more.