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Cervical mucus is a jelly like substance produced by tiny glands in the cervix called cervical crypts. It has a protective function and may prevent bacteria from getting into the uterine cavity. The mucus changes, predictable and cyclically during the menstrual cycle. During the first half of the cycle, before ovulation, when the estrogenic hormones are produced by the cervical glands becomes watery, copious, clear & stretchy. Sperm can penetrate this watery mucus easily, and when intercourse takes place, sperm swim through the mucus rapidly into the uterus. After ovulation, the quality of the mucus changes because the corpus leutum of the ovary now starts to make the hormone progesterone. Mucus produced under the influence of progesterone is thicker, sticker & its quantity is reduced. Sperm cannot swim through this mucus and it forms a barrier to sperm entry into the uterine cavity. Even if intercourse occurs at the time when the cervical mucus is at its most favorable, one about in every 2000 sperm enters the mucus. The rest of the sperm remain in the vagina, where they die quickly because of the acidic pH of the vaginal medium. Those sperm that have entered the mucus can survive there for long periods; certainly for several days after intercourse. Once in the cervical mucus, the sperm steadily swim upwards from it into the uterus over a period of 48 to 72 hours. Thus the cervical mucus acts as a sperm reservoir, to be backed on if intercourse does not take place at ovulation. This is why there is no need to have sex everyday in order to conceive! The cervical mucus also acts as a filter and allows only the best sperm to swim through it into the uterus and up towards the egg present in the fallopian tube.
In some women, the cervical mucus may prevent the sperm from moving freely into the uterus. Such a barrier may be because of the following reasons: |
