Question: how many centimeters must the cervix dilate to before a baby can be born?
Answer: The cervix must be 100 percent effaced and 10 centimeters dilated before a vaginal delivery. The first stage of labor and birth occurs when you begin to feel regular contractions, which cause the cervix to open (dilate) and soften, shorten and thin (effacement). This allows the baby to move into the birth canal.