Cervical Mucus: A sperm's best friend
Cervical mucus (CM) is produced by the cervical glands in the cervix. The cervix is at the end of the vagina, it's at the entrance to the uterus. The physical properties of cervical mucus change during the menstrual cycle.
CM regulates fertility. It accepts, filters, prepares, and releases sperm for successful transport to the inside of the uterus, then on to the fallopian tubes, the egg, and fertilization. Cervical mucus is essential to your fertility: No CM, thick CM, "sperm unfriendly" CM, or too little CM means no or little sperms entering the uterus.
Your CM is the thinnest and best shortly before and during ovulation. The best time for sperm transport through the cervical mucus is during the period shortly before and during ovulation when cervical mucus is thin and stretchy (known as Egg White Cervical Mucus, or EWCM).
After ovulation it becomes thick and won't allow any more sperms entering the uterus.
You now know a lot more about your body, which is a huge step toward making the most of your baby-making attempts! Of course, there's much more to do and learn.