Placental Complications

A placenta accreta spectrum is a group of placental abnormalities based on adherence to the placenta, including placenta accreta, increta, and percreta (UpToDate, 2019). Placenta accreta is an abnormal trophoblast invasion of part or all of the placenta into the myometrium of the uterine wall (Obstetric Care Consensus, 2018). Placenta accreta is when the placental villi attach to the myometrium. In placenta increta, the villi penetrate the myometrium; in placenta percreta, the villi penetrate through the myometrium to the uterine serosa or other organs (UpToDate, 2020). The chief risk factors for the placenta accreta spectrum are previous c-sections, previous placenta previa, or previous uterine surgery (Obstetric Care Consensus, 2018). 

The placenta accreta spectrum is often diagnosed with ultrasound. An MRI may be used to evaluate the placenta further, but MRI has not been proven to improve the accuracy of diagnosis.

Women with the placenta accreta spectrum should deliver in an experienced, high-level maternity care center with a multi-disciplinary team (Silver & Barbour, 2015). This team should minimally include experienced obstetricians, maternal-fetal medicine specialists, pelvic surgeons, urologists, interventional radiologists, anesthesiologists, critical care experts, general surgeons, and neonatologists (Obstetric Care Consensus, 2018).  These women should usually deliver between 34 0/7 – 35 6/7 weeks gestation. Earlier delivery may be recommended. Before the woman delivers, she should have pre-op consultations with appropriate providers and have her hemoglobin maximized. All team members should be aware of the time of the scheduled c-section. Cell saver should be used during surgery, and blood products should be available. Postoperative care may require intensive care (Obstetric Care Consensus, 2018). 

Women with the placenta accreta spectrum are at high risk for hemorrhage. A hysterectomy may be necessary to stop hemorrhage during delivery. These women may also have an injury to other organs and require extensive surgery. The fetus is at risk for preterm delivery.

Placenta previa is when the placenta extends over the cervical os. The main risk factors for placenta previa are a previous previa, previous c-sections, or multiple gestations. Placenta previa is diagnosed by ultrasound. The woman may present with vaginal bleeding. A vaginal exam should not be performed on a pregnant woman who is bleeding. An ultrasound should be performed (UpToDate, 2019b).

Placenta previa puts a woman at high risk of antepartum and postpartum hemorrhage. Women with previa are advised not to have sexual intercourse or perform heavy lifting or exercise, as this may increase their risk of bleeding. Actively bleeding placenta previa is an obstetric emergency. These women should be stabilized if possible and may need a blood transfusion. If she stabilizes, a woman may not have to deliver at the first sign of bleeding. Women with uncomplicated placenta previa should have a c-section at 36 0/7 – 37 6/7 weeks. If the bleeding is severe and persistent, the delivery may be indicated at any gestational age. The fetus is at risk for preterm delivery (Anderson-Bagga, 2020).

Placental abruption is complete or partial detachment of the placenta before delivery of the fetus. The main findings of placental abruption are bleeding, abdominal pain, and hypertonic uterine contractions. Uterine tenderness and abnormal fetal heart tracing are usually seen with placental abruption. A rupture of maternal vessels is the usual cause of abruption, although rarely the bleeding starts with fetal vessels. Low pressure hemorrhage generally occurs at the periphery of the placenta, is called marginal abruption, and can be self-limiting and stabilize. Lighter vaginal bleeding is seen with this type of abruption. A chronic abruption is a light, intermittent bleeding that can lead to fetal growth restriction or oligohydramnios. High pressure hemorrhage generally causes complete or nearly complete separation of the placenta, which can be life-threatening to the mother and fetus (Anderson-Bagga, 2020).

A previous abruption increased the risk of abruption with each pregnancy. Cocaine, smoking, and hypertension are all risk factors for placental abruption.

Placental abruption can cause maternal hemorrhage, disseminated intravascular coagulation (DIC), shock, and death for the mother. The fetus is at risk of fetal growth restriction, preterm delivery, low birth weight, hypoxemia and asphyxia, which can lead to death (Mayo Clinic, 2020). A stable woman with a reassuring fetal status may wait for delivery until after 36 weeks and may deliver vaginally. Unstable women need to deliver emergently by c-section (Anderson-Bagga, 2020).