7. Fluids and their changing roles
There are many reasons why cervical fluid changes so dramatically during a woman’s cycle. Each change has a purpose. During fertile period, the fluid provides sperm a buffer against the vaginal acidity. The fluid’s consistency changes provide enhanced antimicrobial effects.
The fluid can suspend sperm in contact with vaginal tissue, increasing its chances of survival so it is still there when ovulation happens. This fertile liquid is most conducive to sperm movement. It also serves as a filter, allowing only the most sperm to pass through. The sperm with structural or motility variations will also be left behind. Few sperm make it to the uterus. After ovulation, the liquid changes to prevent sperm entering.