202410112313
Status:
Tags: Obstetrics
Placenta accreta spectrum
The pathophysiology of placenta accrete spectrum (PAS) involves abnormal anchoring of placental villi to the uterine myometrium (accreta), invasion into the myometrium (increta), or invasion through the myometrium to the uterine serosa or adjacent tissues (percreta), rather than the decidua.
The International Federation of Gynecology and Obstetrics (FIGO) consensus panel classification system is the most widely accepted pathologic classification of PAS
FIGO classification:
| Grade 1 | Abnormally adherent placenta to the myometrium |
| Grade 2 | Abnormally invasive placenta into the myometrium |
| Grade 3 | Abnormally invasive placenta through the myometrium |
| Subtype 3a | Limited to the uterine serosa |
| Subtype 3b | Urinary bladder invasion |
| Subtype 3c | Invasion of other pelvic tissues or organs |
PAS presents a substantial risk for PPH and maternal morbidity from anemia, coagulopathy, blood product transfusion, acute kidney injury, gravid hysterectomy, intensive care admission, and death, with risk increasing in proportion to the degree of placental invasion
Prior cesarean delivery in the context of a current placenta previa is one of the most significant risk factors for invasive placentation.
A history of a disrupted and potentially scarred endometrium (i.e., from myomectomy, dilation and curettage, hysteroscopy, endometrial ablation, and Asherman’s syndrome) also contributes to the development of PAS
Dx: USG / MRI
Surgical planning
Cesarean delivery involving PAS can be very surgically complex, given the distorted anatomy in the narrowest part of the pelvis and proximity to the bladder, ureters, and major pelvic vasculature
Delivery is usually timed between 35+0 to 36+6 weeks gestation in order to balance the risks of premature delivery with the risk of bleeding with unplanned preterm labor.
In the United States, cesarean hysterectomy is the definitive treatment for PAS recommended by ACOG
Conservative management can result in substantially less blood loss, fewer to no transfusions, and a lower rate of organ injury and severe morbidity. However, conservative management can also be associated with significant risks of infection (12 - 66%), delayed bleeding (10 - 53%), and non-PPH-related severe morbidity (4 - 6%)
Endovascular interventions, including those targeting the uterine arteries, internal iliac arteries, the infrarenal abdominal aorta, and multivessel occlusions, have been studied to assess the impact on blood loss. Although various studies suggest a trend toward lower blood loss with endovascular intervention, the reductions are not of sufficient clinical relevance to warrant routine application
In a recent systematic meta-analysis of endovascular interventional modalities in PAS in 69 studies, only abdominal aortic balloon occlusion was found to significantly decrease blood loss
Anaes planning
Since patients with PAS may be anemic if they have experienced antepartum bleeding from a previa, they may benefit from antepartum iron/hemoglobin optimization. If patients decline blood product transfusion, blood conservation strategies should be discussed preoperatively and utilized.
Historically, GA has been preferred for PAS cases, given
- potential for massive transfusion,
- a progressively edematous airway if the need to convert to GA arises mid-case,
- risk for developing coagulopathy,
- avoidance of sympathectomy-related hypotension from neuraxial anesthesia
Neuraxial anesthesia, particularly in the form of combined spinal-epidural, is often a preferred anesthetic option given that
- it allows for the patient to be awake for the delivery,
- enhances postoperative pain control with neuraxial opioids,
- avoids a potentially difficult airway
Other consideration:
- degree of placental invasion,
- patient comorbidities,
- hospital resources,
- if conversion to GA mid-case would be a/w substantially increased risk