Placental Complications

A placenta accreta spectrum is a group of placental abnormalities based on adherence to the placenta, including placenta accreta, increta, and percreta (American College of Obstetricians and Gynecologists [ACOG], 2018).

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Types of Placenta Accreta

Placenta accreta is an abnormal invasion of trophoblasts into part of a portion of the myometrium, which is the middle and thickest layer of uterine wall (ACOG, 2018). Placenta accreta occurs when the placental villi attach to the myometrium (Silver, 2024). In placenta increta, the placental villi actually penetrate the myometrium (Silver, 2024). In placenta percreta, the placental villi fully penetrate through the myometrium layer and into the uterine serosa and/or other internal organs (Silver, 2024). The chief risk factors for the placenta accreta spectrum are (ACOG, 2018):

• Previous cesarean sections
• Previous placenta previa
• Previous uterine surgery

The placenta accreta spectrum is often diagnosed with ultrasound (Rathburn & Hildebrand, 2022). An ultrasound may suggest placenta accreta in the first trimester but is more often found in the second and third trimester. An ultrasound that does not show placenta accreta does not mean that there is not one. It is important to also consider risk factors (ACOG, 2018). 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 (ACOG, 2018). This team should minimally include experienced obstetricians, maternal-fetal medicine specialists, neonatologists, pelvic surgeons, urologists, anesthesiologists, critical care experts, interventional radiologists, and general surgeons (ACOG, 2018).

Women with placenta accreta spectrum should usually deliver between 34 0/7 to 35 6/7 weeks gestation. Earlier delivery may be recommended. Before the woman delivers, she should have pre-operative consultations with appropriate providers and have her hemoglobin maximized. All team members should be aware of this condition at the time of the scheduled cesarean section. A surgical suite may be more appropriate with extra surgeons to assist. This may include obstetricians, anesthesiologists, pelvic surgeons, gynecologic oncologists, general surgeons, trauma surgeons, neonatologists, and critical care experts. A cell saver, a device that collects and then returns a patient’s blood back to them, may be used during surgery, and blood products should be available, with the blood bank being aware of the patient. Postoperative care may require intensive care (ACOG, 2018).

These women are at high risk for hemorrhage. A hysterectomy may be necessary to stop hemorrhage during delivery. A massive transfusion may be initiated, and tranexamic acid may be given prophylactically (ACOG, 2018). These women may also have an injury to other organs and require extensive surgery. The fetus is at risk for complications due to preterm delivery.

Placenta previa is when the placenta extends over the cervical os. The previa may be partial or complete. The main risk factors for placenta previa are (Anderson-Bagga & Sze, 2023):

• Previous placenta previa
• Previous cesarean section(s)
• Multiple pregnancies
• Smoking
• Cocaine use
• Prior dilation and curettage
• Assisted reproductive technology

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Types of Placenta Previa

Placenta previa is diagnosed by ultrasound. A partial placenta previa may resolve as the pregnancy advances. 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 and should also look for placenta accreta spectrum (Lockwood & Russo-Stieglitz, 2024).

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 cesarean section at 36 0/7 to 37 6/7 weeks. If the previa is found at 36 weeks or greater, delivery by cesarean is recommended at that time. If the bleeding is severe and persistent, the delivery may be indicated at any gestational age. The patient with a placenta previa is at risk for postpartum hemorrhage, which can require blood transfusions, hysterectomy, and intensive care after delivery. The fetus is at risk for complications from preterm delivery, such as low birth weight, lower APGAR scores, and respiratory distress syndrome (RDS) (Anderson-Bagga & Sze, 2023).

Placental abruption is complete or partial detachment of the placenta after 20 weeks gestation but before delivery of the fetus.

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Types of Placental Abruption

(*Please click on the image above to enlarge.)

The main findings of placental abruption are (Ananth & Kinzler, 2024):

• Bleeding
• Abdominal pain
• Hypertonic uterine contractions

Uterine tenderness and abnormal fetal heart tracing are also usually seen with placental abruption (Ananth & Kinzler, 2024).

A concealed abruption occurs when blood accumulates behind the placenta (Schmidt et al., 2022). It may not cause obvious bleeding, but the maternal vital signs, including hypotension and/or tachycardia, as well as abnormal lab work may indicate a concealed abruption (Schmidt et al., 2022).

A rupture of maternal vessels tearing away from the placenta is the usual cause of abruption, although rarely the bleeding starts with fetal vessels. Blood accumulates between the uterine wall and placenta. Low pressure hemorrhage generally occurs at the periphery of the placenta, is often 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 (Ananth & Kinzler, 2024).

The risk factors for a placental abruption include(Schmidt et al., 2022):

• Previous abruption not caused by trauma
• Hypertension
• Cocaine use during pregnancy
• Smoking
• Polyhydramnios
• Multiple gestation pregnancy
• Preeclampsia
• Sudden uterine decompression
• Age > 35
• Trauma (ex. abdominal trauma)

Placental abruption can cause maternal hemorrhage, disseminated intravascular coagulation (DIC), shock, and death for the mother. The fetus is at risk of preterm delivery, fetal growth restriction, low birth weight, and hypoxemia and asphyxia, which can lead to death (Mayo Clinic Staff, 2022b). 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, unless a vaginal birth occurs rapidly, which is possible because of excessive contraction (Schmidt et al., 2022). As with the above conditions, this patient is at risk for postpartum hemorrhage. Maternal death and fetal demise can occur, as well as coagulopathy and hysterectomy (Schmidt et al., 2022).

Natalie is a 22-year-old woman who has had 3 babies, all delivered by cesarean section. She does not have custody of these children because of her history of drug use.

Natalie is currently 32 weeks pregnant. She has had limited prenatal care. She smokes and admits to using cocaine earlier in pregnancy and several times over the last month, including earlier today.

Natalie arrives at your labor and delivery complaining of active, severe, bright red vaginal bleeding and abdominal pain that she rates as a 10/10.

Natalie’s Vitals:

• Blood pressure (BP): 100/60
• Heart rate (HR): 135
• Temperature: 98.6°F
• Respiratory rate (RR): 20
• Oxygen saturation (SpO2): 95%

Her cervix is 2cm dilated and 20% effaced.

When you put Natalie on the monitor, the fetal heart tracing shows a category 3 tracing with absent variability and recurrent, late decelerations.

What do you think is happening? What are the priorities for Natalie?

Natalie is likely experiencing a placental abruption, given her symptoms and history of drug use. This woman needs an immediate cesarean section to save her life and the life of the fetus. The team caring for the mother needs to be prepared to provide fluids and blood products to replace what has been lost. The team caring for the baby needs to be prepared for a baby that needs full resuscitation. Additionally, this woman and her baby may have drug withdrawal symptoms after delivery that will need to be monitored.