Placenta Accessory Lobe

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As I have discussed in the main page of this site entitled, “the placenta and the umbilical cord,” the placenta provides oxygen and nutrients to the fetus while removing waste products from the fetus. The placenta is usually one tissue organ, but on rare occasion, the placenta can also have an extra piece of tissue (or lobe) that is attached to the main body of the placenta only by vessels. This extra lobe is known as a succenturiate lobe. The importance of this anatomical variation lies in the fact that sometimes the placenta will be removed or expelled, and on examination by the provider, the placenta will look intact. Unfortunately, the extra placental lobe will remain in the uterus causing heavy vaginal bleeding or postpartum hemorrhage due to the retained piece of placenta.

The incidence of a placental accessory lobe is estimated as one out of 1000-2000. Sometimes the diagnosis of an extra lobe can be made on ultrasound, but not always. A definitive diagnostic test for an accessory placental lobe does not exist. This is a diagnosis to keep in mind if there is postpartum hemorrhage that does not respond to the usual treatment with methergine, pitocin, or cytotec. These medications are often used by your provider to cause the uterus to stop bleeding.

If the medications to stop postpartum hemorrhage do not work and the diagnosis of an accessory lobe is suspected, the provider will most likely attempt a manual removal of the lobe. In this instance, the patient is sedated to minimize the pain. The level of sedation will vary depending on how stable the patient’s blood pressure is with the ongoing vaginal bleeding. Alternatively, the provider may elect to take the patient to the operating room, and perform a dilation and curettage (D&C) where the patient is placed under a general anesthetic or receives a spinal block (if the patient is stable and there is enough time to perform the block before the patient becomes unstable), and the uterine lining is scraped with a sharp or blunt curette.

Some providers feel that there are no known risk factors that increase the incidence of placental accessory lobe while others feel that a first pregnancy and increasing maternal age play a part in this condition. The accessory lobe can be a problem for the fetus if the vessels connecting the extra lobe happen to run over the cervix. This condition is known as vasa previa. Vasa previa can lead to exsanguination of the fetus if the vessels rupture either spontaneously or when the provider performs artificial rupture of membranes (rupture the bag of water). The vessels connecting the extra lobe to the main body of the placenta can also rupture without the occurrence of vasa previa. There is risk of bleeding to the fetus in this situation as well.

Unlike cases where the placenta loses its natural cleavage plane with the uterus or actually invades the uterine muscle (placenta accreta, increta and percreta), the accessory lobe can be easily removed either manually or with a curette so that the possibility of a hysterectomy is almost nonexistent. In some cases, the patient does not immediately have postpartum hemorrhage even with the accessory lobe, and the patient is sent home only to return days or weeks later with sudden onset vaginal bleeding. In addition, the accessory lobe may have degenerated enough that the uterus has become infected (endometritis) and the patient now needs intravenous (IV) antibiotics.

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