Anterior Previa Moves Faster than Posterior Previa

If your previa is anterior, it is on the front part of your uterus. If you previa is posterior, it is on the back part of your uterus. Ask your OB if your previa is anterior or posterior. Anterior previas move more quickly (averaging 2.6 mm per week) than posterior previas (averaging 1.6 mm per week).

Difference in migration of placenta according to the location and type of placenta previa.

Cho JY, Lee YH, Moon MH, Lee JH.


Department of Radiology and Institute of Radiation Medicine, Seoul National University College of Medicine, 28, Yeongeon-dong, Jongno-gu, Seoul 110-744, Korea.



To correlate the incidence and rate of placental migration with the mode of delivery, pregnancy outcome, and maternal complication according to the location (anterior versus posterior) and type of placenta previa (PP).


We prospectively evaluated the placentas of 98 pregnant women with PP or low-lying placenta (LLP) at the prenatal sonographic examination performed between 20 and 27 gestational weeks. We divided the pregnant women into groups according to type and location of PP. Follow-up sonographic examination was performed between 32 and 37 weeks. We compared incidence of migration to the normal position and calculated the migration rate as the migrated distance divided by the weeks of interval between 2 sonographic examinations. We compared the incidences of cesarean section, fetal outcome, and maternal complications during the pregnancy.


The incidence of migration in the group of anterior placentas was significantly higher than that in the group of posterior placentas. The mean migration rate in the anterior group was 2.6 mm/week, whereas that in the posterior group was 1.6 mm/week. The migration rate of incomplete PP was significantly higher than that of LLP. Incidence of cesarean section for nonmigrated PP was significantly higher in the posterior group. The incidences of premature delivery and vaginal spotting were also significantly higher in the posterior group.


Anterior PP and LLP may migrate more often and faster than posterior PP


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