Discharge of cervical mucus plug in mid-pregnancy does not affect the development and survival of the fetus in the uterus and does not require birth control. The cervical mucus plug is a collection of mucus secreted by the cervix to block the cervical os, preventing bacteria from reaching the cervical os through the vagina and then further up into the uterine cavity, invading the baby’s amniotic cavity and causing intrauterine infections in the fetus. However, the cervical mucus plug is only a peripheral protection, the real protection of the fetus from bacteria and viruses is the fetal placenta, which can block most of the bacteria and viruses. The cervical mucus plug is only a peripheral protection, and the cervical mucus plug can be formed again after it is dislodged, which will not affect the fetus. Therefore, the presence of a cervical mucus plug does not require additional birth control.