Predicting Placenta Accreta Spectrum

Abstract

Objectives-The placenta accreta spectrum (PAS) incidence has risen substantially over the past century, paralleling a rise in cesarean delivery (CD) rates. Prenatal diagnosis of PAS improves maternal outcomes. The Placenta Accreta Index (PAI) is a standardized approach to prenatal diagnosis of PAS incorporating clinical risk and ultrasound (US) findings suggestive of placental invasion. We sought to validate the PAI for prediction of PAS in pregnancies with prior CD.Methods-This work was a retrospective cohort study of pregnancies with 1 or more prior CDs that received a US diagnosis of placenta previa or low-lying placenta in the third trimester. Images of third-trimester US with a complete placental evaluation were read by 2 blinded physicians, and the PAI was applied. Surgical outcomes and pathologic findings were reviewed. Placenta accreta spectrum was diagnosed if clinical evidence of invasion was seen at time of delivery or if any placental invasion was identified histologically. International Federation of Gynecology and Obstetrics criteria were used.Results-A total of 194 women met inclusion criteria. Cesarean hysterectomy was performed in 92 (47%), CD in 97 (50%), and vaginal delivery in 5 (3%). Of those who underwent hysterectomy, PAS was histologically confirmed in 79 (85%) pregnancies. Of the remaining 13 who underwent hysterectomy, all met International Federation of Gynecology and Obstetrics grade 1 clinical criteria for PAS. With a threshold of greater than 4, the PAI has a sensitivity of 87%, specificity of 77%, positive predictive value of 72%, and negative predictive value of 90% for PAS diagnosis.Conclusions-Contemporaneous application of the PAI, a standardized approach to US diagnosis, is useful in the prenatal prediction of PAS. Key Words-morbidly adherent placenta; placenta accreta; Placenta Accreta Index; placenta accreta spectrum; placenta increta; placenta percreta P lacenta accreta spectrum (PAS) is a life-threatening obstetric complication that occurs when the placenta abnormally attaches to or invades the myometrium. Once rare, PAS now complicates as many as 1 per 300 pregnancies. [1][2][3] The substantial rise in the incidence of placental invasion over the past century parallels the rise in cesarean deliveries (CDs), a known risk factor for development of PAS. The etiology of PAS remains controversial, with recent evidence suggestive of uterine dehiscence as the cause, rather than placental invasion. 4 The terminology may not be at odds but, rather, may reflect the complex relationship between uterine scar tissue and rapidly growing trophoblastic tissue. Compared to intrapartum diagnosis,

Placenta Accreta Spectrum

“…Predictive models to date suffer from imprecision and unsatisfactory rates of false-negative results (missed diagnoses). 47 It is important to note that the absence of ultrasound findings for PAS does not rule out the diagnosis in patients with previa and clinical risk factors.…”

Prenatal diagnosis of placenta accreta spectrum

“…Several ultrasound scoring or staging systems have been proposed to improve the prenatal diagnosis of PAS and the prediction of surgical outcomes [62,63]. These are not yet widely used in clinical practice, and validation studies are ongoing [64 ▪ –66 ▪ ].…”

Relationship of Placental Vascular Indices with Macroscopic, Histopathologic, and Intraoperative Blood Loss in Placenta Accreta Spectrum Disorders

“…e 3-dimensional (3D) power Doppler has been a widely used tool to improve the PAS diagnosis, much better than 2-dimensional (2D) USG [7]. One of the most commonly used parameters is the placenta accreta index (PAI), a qualitative index that estimates the possibility of PAS using USG [8,9]. However, there are still differences between prenatal ultrasonography, intrasurgical, and histopathological findings.…”