Article snapshot taken from Wikipedia with creative commons attribution-sharealike license.
Give it a read and then ask your questions in the chat.
We can research this topic together.
The Anterior lip refers to the front-most part of the ectocervix, the vaginal portion of the cervix in the female reproductive system.
Obstetrics
During childbirth, the anterior section of the cervix is nearly always the last part of the woman's cervix to be finally taken up into the lower segment of the uterus. An anterior lip occurs when the top of the cervix swells, but the rest of the cervix has completely dilated.
An anterior lip can slow the woman's progress from the 1st to 2nd stage of labor, because the swelling will usually take time to reduce, before enabling the woman's cervix to be pulled up, and around, the baby's head.