Abstract
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. 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. 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%). 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.
Highlights
Placental accreta spectrum (PAS) disorders are a recognized cause of major maternal morbidity and mortality, with a reported prevalence of between 0.01% to 1.1% of pregnancies 1
The aim of this study is to evaluate the effectiveness of a contingent screening program for identification of pregnancies with placenta accreta spectrum (PAS) based on persistent low-lying placenta in the third trimester in women with a history of previous uterine surgery or Cesarean section
A total of 220 women had a final diagnosis of placenta previa at subsequent scan assessments, and 75 (34.1%) of these women were referred to the PAS diagnostic service because of a history of previous uterine surgery
Summary
Placental accreta spectrum (PAS) disorders are a recognized cause of major maternal morbidity and mortality, with a reported prevalence of between 0.01% to 1.1% of pregnancies 1. Previous Cesarean birth is associated with an almost three-fold increase in risk of PAS in the pregnancy compared to those with a previous vaginal delivery 6. PAS is associated with a significant increase in maternal morbidity and mortality from massive peripartum hemorrhage [10,11]. Hemorrhagic morbidity can be significantly reduced when a diagnosis of PAS is made prior to admission at the time of delivery 12. Systematic screening and diagnosis of PAS would permit referral of these high-risk women to tertiary hospitals with specialized multidisciplinary teams experienced in the management of pregnancies complicated by PAS 13,14
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