What Is a Low-Lying Placenta?

What is low-lying placenta and how will it affect my birth?


Peg Plumbo CNM

Peg Plumbo has been a certified nurse-midwife (CNM) since 1976. She has assisted at over 1,000 births and currently teaches in the... Read more

The upper part of the uterus is the most favorable area for placental implantation because it is rich in blood and, therefore, nutrients and oxygen. The lower uterine segment is not and, therefore, it is possible that if the baby implants too low (low-lying placenta), risks of intrauterine growth restriction and preterm labor are much higher.

If the diagnosis is made before the 28th week of pregnancy, chances are excellent that, as the uterus grows upward, the placenta will migrate (move up) with the uterus and no longer be low-lying. If the diagnosis is made in the third trimester, this migration becomes less of a probability. Then what matters is "how low is low?"

During the last trimester, and especially in the last month, the lower uterine segment thins appreciably and pulls up a bit, which is what causes cervical effacement (thinning) and early dilatation. If the placenta is impinging on the lower segment and is not up in the fundus where it is supposed to be, then part of the placenta may dislodge and hemorrhage may occur. This first episode of bleeding is not necessarily fatal to the baby or mother, but this then becomes a very high-risk pregnancy involving bedrest, no intercourse and no internal examinations. The prospect of a cesarean birth is quite high.

A perinatologist and a good ultrasonographer would be the very best caregivers. I hope this has helped.

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