Placental migration

Low lying placenta and placenta previa

Placental migration

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Low lying placenta

Placenta previa is usually diagnosed after 20 weeks of gestation. This is because about 90% cases of low lying placenta in early pregnancy resolves later in pregnancy. This phenomenon is called placental migration.

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Placenta migration

The phenomenon of placental migration occurs when there is change in the position of the placenta with advancing gestational age. There are two hypotheses for this phenomenon:

1)Dynamic placentation- placental attachment points are constantly forming and reforming.

The re-position of the placenta occurs as a response to uterine growth as well as placental growth. As the lower uterine wall forms and the muscle stretch, the stress causes the attachments in this area (lower uterine) to degrade. As those attachments degrade, new attachment points are formed higher in the uterus in areas that is not subjected to the same kind of growth stress, thus the placeta ‘move’ through degradation and re-formation.

2)Trophotropism- placenta migrates to find best blood supply.

As the uterus grows, the lower part of uterine wall get stretched and become thin, causing the blood supply in the area thins. The placenta moves upward to the thicker upper uterine wall to get better blood supply.