Second-Trimester Screening for Placenta Accreta in Those With Prior Cesarean Delivery [ID: 1380253

Abstract

INTRODUCTION: Our objective was to determine whether placental evaluation in the second trimester is sufficient to look for evidence of placenta accreta in those with prior cesarean delivery (CS). METHODS: Those with prior CS who underwent routine ultrasound (US) at 18–22 weeks in 2021 and delivered in our hospital were identified. Records were reviewed for history and US findings, and delivery records were reviewed to identify those with clinical or pathological evidence of accreta. Fisher’s exact test and Mann-Whitney U were used for statistical comparison. RESULTS: Eight hundred seventy-one patients were included, including 145 (17%) with multiple CS. There were 11 with confirmed accreta (1.3%): 7 requiring hysterectomy and 4 with myometrial fibers on placental pathology. Of 11 cases of accreta, only 4 (36%) had US findings in the second trimester, representing 57% of cases requiring hysterectomy. Cases without suspicious second-trimester findings all had other major risk factors, such as previa (n=3) or additional uterine scars such as prior B-Lynch suture (2), “T” incision (1), and Asherman syndrome (1). Overall, second-trimester US was accurate in 99.1% of cases. Of 8 inaccurate cases (7 false negative, 1 false positive) previa was noted in 4 (50%), versus 7.4% with accurate assessment (P=.002). There was no relationship between age, body mass index, or number of prior CS and accuracy of second-trimester US. CONCLUSION: Ultrasound findings were not identified in the second trimester in the majority of cases with accreta, although findings were noted in the majority requiring hysterectomy. All cases without second-trimester findings had previa or additional risk factors for scarring. Third-trimester US to screen for placenta accreta may not be necessary in all those with prior CS if second-trimester US is normal. Those at highest risk should undergo third-trimester imaging. If there is a selective approach to third-trimester US, a detailed history is important in identifying those with risk factors.