Midtrimester sonographic placenta previa thickness is associated with persistence at delivery

Abstract

Studies suggest placental thickness on 2D ultrasound in midtrimester placenta previa correlates with placenta accreta spectrum. Studies have yet to determine if midtrimester placental thickness is associated with persistent previa at delivery. Single-center retrospective cohort of singleton gestations with previa diagnosed at 18-24 weeks delivering between 2015-2019. The thickest portion of the placenta was measured three times in a longitudinal plane on transabdominal imaging to determine placental thickness. We defined three cohorts: 1) thick placenta (>1 standard deviation above the mean), 2) thin placenta (>1 standard deviation below the mean), and 3) average placenta (within 1 standard deviation above or below the mean). Primary outcome was placenta previa persistence at time of delivery. Secondary outcomes included placenta previa resolution, postpartum hemorrhage, cesarean delivery (CD), placenta accreta spectrum, and composite for maternal morbidity (use of Bakri balloon, B-lynch, or O’Leary, peripartum hysterectomy, dilation & curettage, blood transfusion, ICU admission, or death). In all analyses, average placental thickness was used as the base comparator. Of 239 pregnancies with midtrimester previa, 34 had thin, 166 had average, and 39 had thick placentas. Patients with thick placenta were older, more likely to have prior CD, chronic hypertension, fibroid uterus, and delivery at an earlier gestational age (Table1). After adjusting for confounders, thick placenta was associated with persistent previa at delivery (aOR 6.60, 95%CI 3.02-14.40) and thin placenta was associated with resolved previa at delivery (aOR 2.40, 95%CI 1.23-4.71) (Table 2). Placental thickness was not associated with the remainder of the outcomes. At diagnosis of midtrimester previa, thick and thin placenta are associated with persistent and resolved previa at time of delivery, respectively. This suggests placental thickness may assist with risk stratification. Future studies are needed to determine the normal distribution of placental thickness percentiles by gestational age.View Large Image Figure ViewerDownload Hi-res image Download (PPT)