The placenta begins to form in the first weeks of pregnancy. Normally, it attaches to the uterine wall, but if it attaches abnormally, it is called placenta accreta. There are three forms of placenta accreta, classified based on how deeply the placenta embeds; in most cases, embedding deeper leads to more severe complications. According to the American Pregnancy Association, about one out of every 2,500 pregnancies is affected by some form of placenta accreta.
Placenta accreta is considered a high-risk pregnancy complication, and the issue is most critical during and after delivery. Because the placenta is so deeply attached, it does not detach after childbirth as it would in a normal pregnancy. This drastically increases the risk of severe blood loss after delivery.
Placenta accreta has a spectrum of severity. When the placenta attaches so firmly that it becomes embedded in the uterine muscle wall, doctors diagnose placenta increta. The most severe form, placenta percreta, occurs when the placenta grows through the uterus and infiltrates nearby organs, most commonly the bladder.
Generally, placenta accreta does not present with any symptoms, although it may be detected during a routine ultrasound. In extreme cases of placenta percreta involving the bladder, the woman can experience abdominal pain or blood in the urine. Another pregnancy complication called placenta previa often develops alongside placenta accreta. The former typically presents with vaginal bleeding and can lead doctors to discover placenta accreta.
The cause of placenta accreta is not well understood, but the widely accepted hypothesis is that it results from defects in the endometrial-myometrial interface. This leads to scarring that allows the placenta to attach deeper than usual. This theory, however, does not explain why placenta accreta can occur in women who are pregnant for the first time or have never had uterine surgery or scarring.
The most common risk factor for placenta accreta is a previous cesarean delivery and the risk increases with each subsequent c-section. Additional risk factors include carrying multiples, previous uterine surgeries, advanced maternal age, and diagnosis of placenta previa.
Diagnosing placenta accreta early in pregnancy is ideal because it gives the medical team a chance to adequately prepare for delivery. Ultrasound is the most common diagnostic tool. Most diagnoses are not possible until the second or third trimester. More than 80 percent of women with placenta accreta have placenta previa, which ultrasound can also diagnose.
Hemorrhaging is the most common and dangerous complication of placenta accreta for the mother. This occurs either from the associated placenta previa or from attempts to deliver or remove the placenta from the uterine wall. Careful management is key, as hemorrhaging is a life-threatening situation. Vaginal delivery is not always possible, and most doctors will recommend a cesarean section if the condition is found before labor. In the event of uncontrollable hemorrhage, the woman may require a blood transfusion and a hysterectomy to stop the bleeding.
Because placenta accreta has significant risks associated with labor, delivery is scheduled prematurely. In most cases, this is the safest option for both mother and baby. Depending on the severity, most deliveries are scheduled after 34 weeks of gestation. Premature babies of this age are usually admitted to a NICU, but their overall prognosis is good, and they have the same chances of being healthy as a baby born at term.
Early knowledge of placenta accreta is the best-case scenario because it allows the medical team to plan and manage interventions and outcomes rather than having to react in an emergency. The medical team consists of obstetricians, maternal-fetal health specialists, urologists, critical care experts, neonatologists, surgeons who specialize in female pelvic medicine, and nurses experienced in this area. Delivery should occur in a maternity center or hospital equipped to handle high-risk pregnancies and deliveries.
One way to reduce the risk of placenta accreta is to only have cesarean deliveries when they are medically necessary, and otherwise wait until labor naturally occurs. If you have had a c-section, you may still be able to have your next baby vaginally, depending on the type of incision and your overall health.
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