Effectiveness of contingent screening for placenta accreta spectrum disorders based on persistent low-lying placenta and previous uterine surgery

Abstract

Objectives: Maternal mortality related to placenta accreta spectrum (PAS) disorders remains substantial when diagnosed unexpectedly at delivery. The aim of this study was to evaluate the effectiveness of a routine contingent ultrasound screening program for PAS. Methods: This was a retrospective study of data obtained between 2009 and 2019, involving two groups: a screening cohort of unselected women attending for routine mid-trimester ultrasound assessment and a diagnostic cohort consisting of women referred to the PAS diagnostic service with a suspected diagnosis of PAS. In the screening cohort, women with a low-lying placenta at the mid-trimester assessment were followed up in the third trimester, and those with a persistent low-lying placenta (i.e. placenta previa) and previous uterine surgery were referred to the PAS diagnostic service. Ultrasound assessment by the PAS diagnostic service consisted of two-dimensional grayscale and color Doppler ultrasonography, and women with a diagnosis of PAS were usually managed with conservative myometrial resection. The final diagnosis of PAS was based on a combination of intraoperative clinical findings and histopathological examination of the surgical specimen. Results: In total, 57 179 women underwent routine mid-trimester fetal anatomy assessment, of whom 220 (0.4%) had a third-trimester diagnosis of placenta previa. Seventy-five of these women were referred to the PAS diagnostic service because of a history of uterine surgery, and 21 of 22 cases of PAS were diagnosed correctly (sensitivity, 95.45% (95% CI, 77.16–99.88%) and specificity, 100% (95% CI, 99.07–100%)). Univariate analysis demonstrated that parity ≥ 2 (odds ratio (OR), 35.50 (95% CI, 6.90–649.00)), two or more previous Cesarean sections (OR, 94.20 (95% CI, 22.00–656.00)) and placenta previa (OR, 20.50 (95% CI, 4.22–369.00)) were the strongest risk factors for PAS. In the diagnostic cohort, there were 173 referrals, with one false-positive and three false-negative diagnoses, resulting in a sensitivity of 96.63% (95% CI, 90.46–99.30%) and a specificity of 98.81% (95% CI, 93.54–99.97%). Conclusions: A contingent screening strategy for PAS is both feasible and effective in a routine healthcare setting. When linked to a PAS diagnostic and surgical management service, adoption of such a screening strategy has the potential to reduce the maternal morbidity and mortality associated with this condition. However, larger prospective studies are necessary before implementing this screening strategy into routine clinical practice. © 2020 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.