WebMD explains that the bloody mucus plug coming out during pregnancy is a sign of labor. However, WebMD also notes that the mucus plug sometimes comes out two weeks prior to other signs of labor beginning.
Mayo Clinic also states that the loss of the mucus plug during pregnancy means that labor is about to begin or that it is days or weeks away. The mucus plug is in place to prevent bacteria from entering the uterus and causing an infection. It develops during pregnancy as mucus accumulates in the cervix. One of the first signs of labor is the cervix softening and thinning. This is known as effacement, and the process continues to allow for a vaginal delivery. When effacement occurs between 37 and 40 weeks of pregnancy, some women may experience spot bleeding, an increase in discharge or a loss of their mucus plug.
Mayo Clinic advises that women who experience heavy bleeding should contact their health care provider. According to WebMD, there are other signs of labor that women can look out for. Feeling the urge to urinate more often is a sign that labor isn't far away. Signs of imminent labor include the water breaking and the woman experiencing contractions.