During pregnancy, the placenta is normally attached to the upper wall of the uterus. A placenta that forms low in the uterus without overlapping the cervical opening is referred to as a low-lying placenta. It is not a high-risk condition. It often gets better on its own as the pregnancy progresses.
If you have a low-lying placenta early in pregnancy, there is a good chance that it will get better on its own. As the lower uterus enlarges, the placenta's relative position will shift away from the cervix.
But when the placenta does overlap the cervix, it is called placenta previa. Placenta previa can bleed heavily during labor. The good news is that about 90% of cases diagnosed before the 20th week no longer overlap the cervix by the end of the pregnancy.footnote 1
Medical Review:Sarah Marshall MD - Family Medicine & Adam Husney MD - Family Medicine & Kathleen Romito MD - Family Medicine & Rebecca Sue Uranga
Williams DE, Pridjian G (2011). Obstetrics. In RE Rakel, DP Rakel, eds., Textbook of Family Medicine, 8th ed., pp. 359-401. Philadelphia: Saunders.