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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 predictably and cyclically during the menstrual cycle. During the first half of the cycle before ovulation, when the hormone estrogen is produced in ever increasing amounts, the mucus made by the cervical glands becomes watery and copious. Sperm can penetrate the watery mucus easily, and when intercourse takes place, they swim through it into the uterus.
After ovulation the quality of the mucus changes because the corpus luteum of the ovary now starts to make the hormone progesterone. Mucus produced under the influence of progesterone is thicker, stickier and 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 the cervical mucus is at its most favorable, only about 1 in every 2000 sperm enter the mucus. The rest of the sperm remain in the vagina, where they die, because of the acidic pH of the vagina. Those sperm that have entered the mucus can survive there for long periods - certainly for several days after intercourse. Once in the cervical mucus, they 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 banked on if intercourse does not take place at ovulation. This is why you don't 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.
© Dr. Aniruddha Malpani and Dr. Anjali Malpani www.drmalpani.com
Credits: How to Have a Baby: Overcoming Infertility
