Throughout pregnancy a mucus plug blocks the opening to the cervix to prevent bacteria from entering. Before labor, this mucus plug is expelled so that the cervix can open to allow the baby to pass through to prepare for delivery.
Passing a mucus plug is a sign that your cervix is dilating and your body is starting to prepare for birth. Labor could be hours, days, or even weeks away as the cervix gradually opens over time.
A mucus plug may be clear, slightly pink or blood tinged in color. It may be stringy mucus or sticky discharge. Some women may not even notice the loss of their mucus plug because there is already so much vaginal discharge during pregnancy.
You should call your doctor immediately if your discharge suddenly becomes bright red and the amount is more than an ounce (about two tablespoons). You could be experiencing placenta previa or placental abruption.
Placenta previa is when the placenta lies low in the uterus, it may partly or completely cover the cervix which causes vaginal bleeding. Placenta previa occurs in 1 of 200 women.
The placenta may detach from the uterine wall before or during labor, this is called placental abruption and usually only 1% of pregnant women have this problem.
Reprinted with permission from American Pregnancy Association