Prenatal identification of invasive placentation using ultrasound in women with placenta previa and prior cesarean delivery

Objective: To evaluate the performance of ultrasound for antenatal identification of invasive placentation in women with placenta previa in the setting of prior cesarean delivery. Study design: This was a multicenter, retrospective, cohort study. Singleton pregnancies at risk of placenta accreta because of persistent placenta previa in the setting of prior cesarean delivery who delivered at four centers, from January 2010 to May 2020, were included in the study. For this study, pregnancies with diagnosis of accreta, increta, or percreta were considered under the umbrella term of placenta accreta. All women with placenta previa identified in the second trimester had a follow-up ultrasound at 32-34 weeks. Only those with prior cesarean delivery were considered at risk of placenta accreta. Women were considered with suspected accreta in case of suspected prenatal ultrasound. Women with suspected placenta accreta had delivery planned via cesarean hysterectomy at 34+0 - 35+6 weeks, without any attempt to remove the placenta. The primary endpoint of the study was the performance of ultrasound for antenatal identification of invasive placentation. The following ultrasound signs were evaluated: placenta lacunae; loss of clear space; increased vascularity between myometrium and placenta; intracervical lake; rail sign; uterovesical hypervascularity; increased vascularity in the inferior part of the lower uterine segment potentially extending into the parametrial region; and disruption of bladder-myometrial interface.<br /> Results: 180 singleton pregnancies with placenta previa in the setting of prior cesarean delivery were identified. Of them, 155 (86.1%) had antenatal suspected placenta accreta based on ultrasound, having at least one sign of invasive placentation. Of the 155 suspected cases, 99 had confirmed placenta accreta at the time of delivery. Among the 99 cases of confirmed placenta accreta, all of them had at least one sign of invasive placentation at ultrasound. Among the 81 cases with placenta previa, prior cesarean delivery, without placenta accreta, 25/81 (30.9%) had ultrasound scan negative for sign of invasive placentation, and 56/81 (69.1%) had at least one sign of invasive placentation). In particular, 12/81 (14.8%) had placenta lacunae, 16/81 (19.8%) had loss of clear space, 20/81 (24.7%) had increased vascularity between myometrium and placenta, 9/81 (11.1%) had intracervical lake, 14/81 (17.3%) had rail sign, 14 (17.3%) had uterovesical hypervascularity, 5/81 (6.2%) had increased vascularity in the inferior part of the lower uterine segment potentially extending into the parametrial region, 8/81 (9.9%) had disruption of bladder-myometrial interface. In the group of women with confirmed placenta accreta, the most common sign recorded was the disruption of bladder-myometrial interface, being recorded in 88/99 women. Disruption of bladder-myometrial interface had the highest sensitivity in detection placenta accreta. Women with disruption of bladder-myometrial interface at ultrasound had 73-fold increase in the risk of placenta accreta compared to those who did not. Conclusion: Prenatal ultrasound has an excellent diagnostic accuracy in identifying invasive placentation in women with placenta previa and prior cesarean delivery.