Assessment of placenta accreta spectrum at vaginal birth after cesarean delivery

Previous cesarean delivery is a risk factor for developing placenta accreta spectrum in a subsequent pregnancy and patients with antenatally suspected placenta accreta spectrum frequently undergo planned cesarean hysterectomy. There is a paucity of data regarding unsuspected placenta accreta spectrum among patients undergoing trial of labor after cesarean delivery for attempted vaginal birth after cesarean delivery.

This study aimed to investigate the incidence, characteristics, and delivery outcomes of patients with placenta accreta spectrum diagnosed at the time of vaginal birth after cesarean delivery.

The Healthcare Cost and Utilization Project's National Inpatient Sample was retrospectively queried to examine 184,415 patients with a history of low transverse cesarean delivery who had vaginal delivery in the current index hospital admission between 2017 and 2020. Those with placenta previa, previous vertical cesarean delivery, other uterine scars, and uterine rupture were excluded. This study identified placenta accreta spectrum cases using the World Health Organization International Classification of Disease, Tenth Revision, codes of O43.2. Coprimary outcomes were (1) the incidence rate of placenta accreta spectrum at vaginal birth after cesarean delivery; (2) clinical and pregnancy characteristics related to placenta accreta spectrum, assessed with multivariable binary logistic regression model; and (3) delivery outcomes associated with placenta accreta spectrum by fitting propensity score adjustment. The secondary outcome was to conduct a systematic literature review using 3 public search engines (PubMed, Cochrane, and Scopus). Data on incidence rate and maternal morbidity related to placenta accreta spectrum at vaginal birth after cesarean delivery were evaluated.

The incidence rate of placenta accreta spectrum at vaginal birth after cesarean delivery was 8.1 per 10,000 deliveries. Most placenta accreta spectrum cases were placenta accreta (83.3%). In a multivariable analysis, older maternal age, tobacco use, preeclampsia, multifetal pregnancy, fetal anomaly, preterm premature rupture of membrane, chorioamnionitis, low-lying placenta, and preterm delivery were associated with an increased risk of placenta accreta spectrum (all, P<.05). Of these factors, low-lying placenta had the largest odds for placenta accreta spectrum (526.3 vs 7.3 per 10,000 deliveries; adjusted odds ratio, 35.02; 95% confidence interval, 18.19-67.42). Patients in the placenta accreta spectrum group were more likely to have postpartum hemorrhage (80.0% vs 5.5%), blood product transfusion (23.3% vs 1.0%), shock or coagulopathy (20.0% vs 0.2%), and hysterectomy (43.3% vs <0.1%) than those without placenta accreta spectrum (all, P<.001). In a systematic literature review, a total of 212 studies were screened, and none of these studies examined the incidence and morbidity of placenta accreta spectrum at vaginal birth after cesarean delivery.

This nationwide assessment suggests that although placenta accreta spectrum with vaginal birth after cesarean delivery is uncommon (1 of 1229 cases), the diagnosis of placenta accreta spectrum at vaginal birth after cesarean delivery is associated with significant maternal morbidity. In addition, the data suggest that low-lying placenta in the setting of previous low transverse cesarean delivery warrants careful evaluation for possible placenta accreta spectrum before a trial of labor.