The following is a summary of “Role of transvaginal ultrasound in the third-trimester evaluation of patients at high risk of placenta accreta spectrum at birth,” published in the October 2023 issue of Obstetrics and Gynecology by Jauniaux, et al.

The use of transvaginal ultrasound imaging has become indispensable in evaluating the lower uterine segment and cervix anatomy during prenatal care. However, there was a paucity of comprehensive data regarding the efficacy of transvaginal ultrasound in managing patients at a heightened risk of experiencing the placenta accreta spectrum during childbirth. For a study, researchers sought to examine the role of transvaginal sonography in the third trimester in predicting outcomes for patients with an elevated likelihood of facing placenta accreta spectrum during childbirth.

The research adopted a retrospective approach, analyzing data prospectively collected from patients with a singleton pregnancy and a history of at least one previous cesarean delivery. Additionally, patients diagnosed prenatally with an anterior low-lying placenta or placenta previa, who underwent elective delivery after 32 weeks of gestation, were included. Each patient underwent at least one comprehensive ultrasound examination, encompassing both transabdominal and transvaginal scans, within two weeks preceding delivery. Notably, two proficient operators, unaware of clinical data, provided a binary judgment on the likelihood of placenta accreta spectrum, categorizing it as low or high probability. They were also tasked with predicting the primary surgical outcome, distinguishing between conservative measures and peripartum hysterectomy. The confirmation of accreta placentation occurred when one or more placental cotyledons couldn’t be digitally separated from the uterine wall either at delivery or during the gross examination of hysterectomy or partial myometrial resection specimens.

The study encompassed 111 patients, revealing abnormal placental tissue attachment in 76 individuals (68.5%) at birth. Histologic examination confirmed creta (superficial villous attachment) in 11 cases and increta (deep villous attachment) in 65 cases. Notably, 72 patients (64.9%) underwent peripartum hysterectomy, including 13 cases without evidence of placenta accreta spectrum at birth, primarily due to challenges in reconstructing the lower uterine segment and/or excessive bleeding. A significant difference in placental location distribution (X²=12.66; P=.002) was observed between transabdominal and transvaginal ultrasound examinations. However, both techniques demonstrated similar likelihood scores in identifying accreta placentation confirmed at birth. On transabdominal scan, only a high lacuna score exhibited a significant association (P=.02) with an increased likelihood of hysterectomy. Conversely, on transvaginal scan, associations between the need for hysterectomy and specific factors were identified: thickness of the distal part of the lower uterine segment (P=.003), changes in cervix structure (P=.01), increased vascularity in the cervix (P=.001), and the presence of placental lacunae (P=.005). The odds ratio for peripartum hysterectomy was 5.01 (95% CI, 1.25–20.1) for a very thin (<1-mm) distal lower uterine segment and 5.62 (95% CI, 1.41–22.5) for a lacuna score of 3+.

The inclusion of transvaginal ultrasound examination emerges as a valuable contribution to prenatal management and the anticipation of surgical outcomes among individuals with a history of prior cesarean delivery, irrespective of the presence of ultrasound signs indicating placenta accreta spectrum. The assessment of the lower uterine segment and cervix through transvaginal ultrasound should be integrated into clinical protocols for the comprehensive preoperative evaluation of patients facing the prospect of complex cesarean delivery. The integration was pivotal for refining risk assessments and tailoring interventions in obstetric care.

Source: ajog.org/article/S0002-9378(23)00311-3/fulltext