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Placenta Previa

Placenta Position – Low Lying, Marginal and Previa

Placenta previa means placenta first. For safe labor the baby’s head is supposed to be first. Placenta previa is always a problem at delivery, and sometimes causes pregnancy complications earlier.

previaPlacental position is determined by ultrasound. We first look for placenta location at the 20 week ultrasound. It is common for a placenta to appear in a low position this early in pregnancy. Its not until 28 or 30 weeks that ultrasound can be sure the placenta is too close to the cervix. Low is considered to be within 2 centimeters of the cervical opening.

If the placenta is more than 2 cm away on any ultrasound measurement, there is no placenta previa and Labor is general safe for a placenta more than 2 cm away from the cervix.

If the placenta is still low at 28 weeks then we need to consider the possibility of complications, both before and during labor. The primary complication from a placenta previa is painless vaginal bleeding. Pregnant women with a low placenta or placenta previa after 28 weeks should not have sex…orgasm is considered safe however penis in vagina sex is NOT safe.

A pregnant woman with a low placenta or placenta previa and BLEEDING must go to the HOSPITAL.


The next ultrasound is done around 35 weeks to confirm, again, that the placenta is still low or covering the cervix. Delivery for a low or placenta previa is a planned cesarean section, usually between 37 and 38 weeks. The timing of delivery is moved earlier based on the vaginal bleeding: how much and how recent. Patients are admitted to the hospital for observation after an episode of vaginal bleeding. Some women go home a few days after the first episode of bleeding. After the second episode of bleeding, most women will stay until delivery.

Cesarean section can be complicated in women with placenta previa.  This is especially true for patients previously delivered by cesarean section and patients with an anterior placenta. Anterior refers to the front location of the uterus, which is the location of the uterine scar.

When there is bleeding from placenta previa it is MOMMY blood, not baby blood.

A low placenta or placenta previa is still a normal functioning placenta. Babies born to mothers with placenta previa are healthy and fully grown. Sometimes bleeding will cause early delivery, so prematurity is the primary baby problem for placenta previa. Sometimes the bleeding is enough to endanger the baby, but usually not.


The other problems and complications from placenta previa are mommy complications which occur after the baby is delivered. There can be enough bleeding to require a blood transfusion. In certain cases the placenta will damage the uterus beyond repair. If a uterus continues to bleed after delivery the mother’s life can be in danger. In this situation, as a last resort, we do hysterectomy to remove the uterus and stop the bleeding. This is a very rare event, but one which we need to understand and for which we must be prepared.

A low placenta at 20 weeks if very common and almost every low placenta at 20 weeks resolves itself prior to delivery. Only very few placentas remain low or previa. A disaster at cesarean delivery, because of placenta previa, is VERY RARE.