Effectiveness of Contingent screening for Placenta Accreta Spectrum disorders based on persistent low-lying placenta and previous uterine surgery

OBJECTIVES: Maternal mortality related to the placenta accreta spectrum (PAS) disorders remain substantial when an unexpected diagnosis is made at delivery. The aim of this study was to evaluate the effectiveness of a routine contingent ultrasound screening program for PAS. METHODS: A retrospective study conducted between 2009 and 2019 involving two groups: a screening cohort of unselected women attending for routine mid-trimester ultrasound assessment and a diagnostic cohort comprised of referrals to the PAS diagnostic service with a suspected diagnosis of PAS in women with placenta previa and previous uterine surgery. Ultrasound assessment by the PAS diagnostic service was comprised of two-dimensional greyscale 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: 57,179 women underwent routine mid-trimester fetal anatomy assessment with a third trimester diagnosis of placenta previa in 220 (0.38%). Seventy-five of these women were referred to the PAS diagnostic service because of a history of previous uterine surgery, where 21 of 22 cases of PAS were correctly diagnosed (sensitivity of 95.45%, 95%CI: 77.16-99.88% and specificity of 100%, 95%CI: 99.07-100%). Univariate analysis demonstrated that 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 96.63% (95%CI: 90.46-99.30%) and specificity 98.81% (95%CI: 93.54-99.97%). CONCLUSION: A contingent screening strategy for PAS is both feasible and effective in a routine healthcare setting. When linked to a placenta accreta 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. Larger prospective studies are necessary before implementing this screening strategy into routine clinical practice. This article is protected by copyright. All rights reserved.