Question: is effacement the same as cervical length?
Answer: Cervical effacement and lower uterine segment changes may predate cervical dilatation. The unaffected cervix in the third trimester usually measures between 3.5 and 4.8 cm in length. Fifty-percent effacement corresponds to a cervical length of 1.5 cm, and 75-percent effacement corresponds to a length of 1.0 cm.