Placenta accreta is a condition where the placenta grows too deeply into the wall of the uterus, failing to detach normally after childbirth. It cannot resolve on its own; the placenta will not spontaneously detach before delivery. This deep implantation prevents the natural separation of the placenta from the uterine wall that typically occurs after birth. The danger lies in the inability of the uterus to expel the placenta, which can trigger severe, life-threatening hemorrhage if separation is attempted during delivery. Early detection through prenatal screening is important for proper management.
Understanding Placenta Accreta Spectrum
The condition is formally classified as Placenta Accreta Spectrum (PAS), reflecting a range of severity based on the depth of placental invasion into the uterine muscle. The mildest and most common form is Placenta Accreta, where the chorionic villi attach firmly to the surface of the uterine muscle (myometrium) without penetrating it deeply. This form accounts for approximately 75% to 78% of all PAS cases.
The next level is Placenta Increta, where the chorionic villi invade deeper into the myometrium. The most severe form, Placenta Percreta, involves the villi penetrating through the entire thickness of the myometrium, potentially invading adjacent organs like the urinary bladder or bowel. The risk of developing PAS increases with a history of previous Cesarean sections, as the placenta may implant over the resulting uterine scar. Another risk factor is placenta previa, where the placenta partially or completely covers the cervix.
Identifying the Condition
The diagnostic process for PAS typically begins with routine prenatal care, especially in pregnancies with known risk factors. Antenatal ultrasound is the primary tool for screening and diagnosis, often performed during the second trimester. Clinicians look for specific imaging signs, such as a “loss of the clear zone,” which is the normal space between the placenta and the uterine wall.
Other indicators on ultrasound include multiple, abnormal vascular spaces within the placenta, sometimes called lacunar spaces, which show turbulent blood flow on Doppler imaging. Magnetic Resonance Imaging (MRI) is often used as a secondary confirmation tool, particularly when ultrasound findings are unclear or when deep invasion, such as Placenta Percreta, is suspected. MRI is useful for assessing the depth of invasion and determining if the placenta has invaded surrounding structures like the bladder wall.
Specialized Care During Pregnancy
Once a diagnosis of Placenta Accreta Spectrum is made, the focus shifts from expecting a natural delivery to preparation for a highly managed birth. Since the condition cannot be reversed during pregnancy, the objective is to safely manage the remainder of the gestation period until the planned delivery. This involves frequent monitoring to detect early signs of complications, such as third-trimester vaginal bleeding or preterm contractions.
Patient counseling is a crucial element, ensuring the patient fully understands the risks and the complex surgical plan. Care and delivery should take place at a specialized tertiary care facility equipped to handle high-risk obstetric hemorrhage. These centers have immediate access to a blood bank capable of massive transfusion protocols, interventional radiologists, and a full multidisciplinary team. The goal of this specialized prenatal management is to avoid unscheduled, emergent delivery, which increases the risk of severe blood loss and maternal complications.
Delivery and Definitive Treatment
The definitive treatment for Placenta Accreta Spectrum is a planned, multidisciplinary surgical delivery. This procedure is typically scheduled in the late-preterm period, often between 34 and 36 weeks of gestation. This timing balances the risk of massive hemorrhage with the risks of prematurity for the baby. Delivering within this window aims to prevent the onset of labor, which could trigger a catastrophic bleed due to attempted placental separation.
The surgical team is extensive, including maternal-fetal medicine specialists, gynecologic oncologists, urologists, and interventional radiologists, all prepared for potential complications. The standard of care for most severe cases is a controlled C-section delivery, followed immediately by a Cesarean hysterectomy. This involves removing the entire uterus with the placenta still attached to prevent the massive hemorrhage that would occur if the placenta were forcibly removed.
While the standard approach is hysterectomy, certain centers may offer conservative or expectant management, which involves leaving the placenta inside the uterus to dissolve over time. This uterine-preserving approach carries risks, including severe vaginal bleeding, infection, and the potential need for a delayed, emergency hysterectomy. Therefore, Cesarean hysterectomy remains the safest and most common treatment to manage the life-threatening risks associated with the condition.