Placenta Accreta Spectrum Prenatal Diagnosis Performance: Are Ultrasound False-positive Results Acceptable in Limited-resources Settings?

Abstract

Objective: The immediate referral of patients with risk factors for placenta accreta spectrum (PAS) to specialized centers is recommended, thus favoring an early diagnosis and an interdisciplinary management. However, diagnostic errors are frequent, even in referral centers (RCs). We sought to evaluate the performance of the prenatal diagnosis for PAS in a Latin American hospital.

Methods: A retrospective descriptive study including patients referred due to the suspicion of PAS was conducted. Data from the prenatal imaging studies were compared with the final diagnoses (intraoperative and/or histological).

Results: A total of 162 patients were included in the present study. The median gestational age at the time of the first PAS suspicious ultrasound was 29 weeks, but patients arrived at the PAS RC at 34 weeks. The frequency of false-positive results at referring hospitals was 68.5%. Sixty-nine patients underwent surgery based on the suspicion of PAS at 35 weeks, and there was a 28.9% false-positive rate at the RC. In 93 patients, the diagnosis of PAS was ruled out at the RC, with a 2.1% false-negative frequency.

Conclusion: The prenatal diagnosis of PAS is better at the RC. However, even in these centers, false-positive results are common; therefore, the intraoperative confirmation of the diagnosis of PAS is essential.

Fig. 1

Imaging findings scheme (ultrasonography or magnetic resonance imaging) in suspected placenta accreta spectrum (PAS) cases. The scheme is used to improve communication between the prenatal diagnosis group (maternal-fetal specialist and/or radiologist) and the surgical group during the planning of the surgical procedure.

Fig. 2

(A and B). Ultrasonography (US) images. (A): Sagittal plane section through the vagina, showing pathological lacunae with turbulent flow toward the cervix. (B): Axial plane section through the abdomen with loss of the uteroplacental interface and pathological placental lacunae; limited visualization due to abundant adipose tissue and scars on the abdominal wall (3 previous cesarean sections). (C to E). Uterus and placenta once resected. (C): Axial plane section at the level of the cervix, at the same level as the US image in A. Severe anatomical distortion can be seen, correlating with the presurgical drawing of the sagittal plane in Figure 1 . (D): Axial section of the lower uterine segment, at a level that corresponds to the US image in B and the level marked with an arrow in E. Severe thinning of the myometrium can be seen in the anterior part of the uterus, with areas of serosal loss, probably related to the surgical procedure. (E): Anterior face of the uterus showing correlation with the presurgical drawing of the coronal plane section on Figure 1 .

Fig 3

Flowchart of patients referred due to suspected placenta accreta spectrum (PAS) to a referral center (RC) and performance of prenatal diagnostic images. Abbreviations: FN, false-negative; FP, false-positive. MRI, magnetic resonance imaging; RH, referring hospital; US, ultrasonography. False-positive and FN values were calculated by comparing the presurgical diagnosis issued by the RH and the RC with the final postoperative diagnosis (applying clinical FIGO staging criteria and histopathology); * median (interquartile range); ** Confirmed or excluded PAS by intraoperative or histological findings. *** Percentage of FPs excluding patients for whom it was not possible to perform US in RC due to being admitted in an emergency situation.