First-trimester ultrasound diagnostic features of placenta accreta spectrum in low-implantation pregnancies

OBJECTIVE Low implantation pregnancy is an important marker for the diagnosis of placenta accreta spectrum in the first trimester. Many grayscale and color Doppler markers have been well defined in the second and third trimesters of pregnancy but not well studied in the first trimester. The aim of this study was to determine if and which placenta accreta spectrum sonographic markers can be used in the first trimester to differentiate patients with low implantation pregnancy who end up developing placenta accreta from those who do not. METHODS This was a retrospective case-control study of pregnancies who delivered at our institution from 2009-2019. Cases represented pregnancies with placenta accreta spectrum who delivered by cesarean hysterectomy and had a first trimester ultrasound with low implantation pregnancy. Controls represented pregnancies with persistent placenta previa without placenta accreta spectrum, who delivered by cesarean section without postpartum hemorrhage and had a first trimester ultrasound with low implantation pregnancy. Sonographic images were reviewed by an investigator blinded to pregnancy outcome and sonography reports. Images were reviewed for presence of abnormal uteroplacental interface, increased lower uterine segment hypervascularity, and placental lacunae, with or without swirling on grayscale or color Doppler. RESULTS 21 cases and 46 controls met the inclusion criteria. Lacunae were present in 18/21 (85.7%) cases and in 7/46 (15.2%) controls (OR 33.4; 95% CI 7.7-144.4, p<.001). The number of lacunae was significantly higher in the cases as compared to the controls with a median of 5 lacunae in the cases as compared to a median of 1 lacunae in the controls (p<.001). The median size of the lacunae was also significantly larger in the cases measuring 10.03mm (IQR 7.3-12.05) compared to 4.15mm (IQR 4.05-5.05) in the controls (p=.001). Lacunae swirling on grayscale or color Doppler was noted only in the cases with 10/12 (83.3%) having swirling on grayscale and 12/12 (100%) having swirling on color Doppler (p <.001). Presence of an abnormal uteroplacental interface was also noted only in the cases at a rate of 17/20 (85.0%, p <.001). Lower uterine segment (uterovesical, subplacental, and/or intraplacental) hypervascularity was present in 14/14 (100%) cases and only 1/12 (8.33%) controls (p <.001). CONCLUSION In PAS-at-risk pregnancies, ultrasound markers of PAS can and should be assessed as early as the first trimester. The use of a first-trimester prenatal ultrasound screening protocol and standardized approach to the ultrasound examination in at-risk mothers may help in increased detection of PAS and in planning for the optimal management of these pregnancies. This article is protected by copyright. All rights reserved.