Five Myths and Facts about Placenta Accreta

December 3, 2015 Brigham and Women's Hospital

Doppler study showing hypervascular accreta.

Doppler study showing placenta accreta.

Placenta accreta occurs when the placenta – the organ that provides nutrients and other support to a developing fetus – attaches too deeply into the uterine wall. This can lead to severe complications at the time of delivery, and much stress for the expectant mother and her family. Dr. Daniela Carusi, Director of Surgical Obstetrics at Brigham and Women’s Hospital, addresses common myths about placenta accreta to help us learn about this serious condition.

Myth #1: Women with placenta accreta hemorrhage at the time of delivery.

Fact #1: Women with accreta are certainly at high risk for bleeding and hemorrhage, which is why expert care is needed. However, accreta can occur in a wide range of circumstances and not every woman will hemorrhage.

The likelihood of a hemorrhage depends on the individual conditions of your placenta. During pregnancy, bleeding and hemorrhage are more related to placenta previa (placenta covering the cervix) than to the accreta. With a previa, large blood vessels around the cervix may bleed in response to contractions, or bleed on their own, though most women with a previa do not hemorrhage. An accreta that develops without previa would be less likely to bleed.

The risk also may be related to how the placenta is treated at the time of delivery. When delivering a baby from a uterus with an accreta, particular care is given to where the incision is made. Many women with accreta will have an up-and-down incision, so as to deliver the baby without disturbing the accreta. If the accreta is low in the uterus, which is usually the case, this incision allows a safe delivery above this area.

In some cases, a hemorrhage is highly likely or even inevitable, but this is not true for all women with accreta. Regardless of the hemorrhage risk, it’s important that well-trained obstetricians who understand your specific needs and risks manage your baby’s delivery.

Myth #2: Women diagnosed with accreta must have a hysterectomy after delivery.

Fact #2: A hysterectomy is a highly effective treatment for minimizing hemorrhage, but is not always necessary. In general, large accretas are most safely managed with a hysterectomy. However, small or “focal” accretas can sometimes be removed without a hysterectomy. In other cases, patients and their doctors may agree that leaving some or all of the accreta in the uterus (rather than removing the uterus) is a reasonable option. These decisions are complicated and require extensive discussion with an experienced obstetrician.

Myth #3: If a woman with placenta accreta does not experience bleeding, it’s safe to carry her baby to term.

Fact #3: The majority of women with placenta accreta need to deliver weeks before their due dates, even if there has been no bleeding. This is often the best option for a controlled delivery, where all risks can be managed safely. If a woman experiences heavy bleeding, an earlier delivery may be especially important.

Delivery with accreta requires a very complex surgery, often with a multidisciplinary team of surgeons, so it is best to deliver your baby as soon as it is safe, in terms of the baby’s health and the mother’s wellbeing. Typically, this occurs at week 34 of gestation (6 weeks before the due date) and no later than week 36-37 of gestation. However, this depends on your specific conditions.

Myth #4: An accreta can be detected on an ultrasound or MRI image before delivery.

Fact #4: An ultrasound or MRI image can usually detect an accreta, but not always. For example, an ultrasound or MRI may detect increased vascularity (or blood flow) that is beyond normal. That could be evidence of a possible accreta. A pregnant uterus, however, always has extra blood flow to some degree. This makes interpreting ultrasound and MRI images particularly challenging. Having images reviewed by a radiologist and obstetrician who are experienced in identifying accreta cases is important, although even then there can be some uncertainty. Women at high risk for accreta should deliver with a team of experienced doctors who are prepared to manage an accreta and possible hemorrhage, even if accreta was not detected on ultrasound or MRI.

Myth #5: A vaginal delivery is not possible with accreta.

Fact #5: Many, if not most, women with accreta also have placenta previa, have had a previous cesarean section, or both. A placenta previa always requires a cesarean section because the placenta is covering the cervix. Similarly, it is usually safest for women with accreta who have had a previous cesarean section to deliver their baby via cesarean again. This is especially true if the placenta is attached to the scar from the previous cesarean. Women who labor after a prior cesarean section are at risk for uterine rupture. The safety of labor with a placenta invading a cesarean section scar has never been evaluated, and the risk of rupture and major hemorrhage may be higher in this situation.

If you do not have a placenta previa, you may be able to deliver vaginally. However, this delivery may be complicated and is at a higher risk for hemorrhage. It is important to talk to an obstetrician with experience in this area before deciding on a vaginal versus cesarean delivery.

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