Cervical Mucus
Cervical mucus appears prior to ovulation. Rising levels of estrogen stimulate the crypts lining the cervical canal to produce mucus. Estrogen reaches its peak production around ovulation day. The estrogen peak corresponds with the mucus peak. Cervical mucus prepares the way for sperm, enabling them to live until ovulation occurs.
Sperm require cervical mucus to live. Sperm, in the absence of cervical mucus, will die within hours or even minutes when deposited in the vagina. In the presence of cervical mucus sperm may live for 3 to 5 days and wait for ovulation to occur. After ovulation rising levels of progesterone cause the cervical crypts to stop producing mucus, since sperm survival is no longer necessary.