Placenta accreta spectrum (PAS) refers to morbidly adherent trophoblastic tissue invading into the gravid uterus and is associated with significant maternal morbidity. The majority of PAS is suspected antenatally, and most patients undergo planned, late-preterm cesarean hysterectomy to reduce the risk of morbidity. Rarely, however, PAS can be incidentally diagnosed at vaginal delivery, but there is a scarcity of data regarding these events.
To examine the incidence, characteristics and outcomes of pregnant individuals with incidentally diagnosed PAS at term vaginal delivery.
This is a retrospective cohort study querying the Healthcare Cost and Utilization Project's National Inpatient Sample. The study population was 8,694,669 term vaginal deliveries from 1/2016-12/2019. Exclusion criteria included prior uterine scar, placenta previa, and preterm delivery. Exposure was assigned by the diagnosis of PAS. The main outcomes were (i) incidence rate, (ii) clinical and pregnancy characteristics, and (iii) maternal morbidity related to unsuspected PAS at vaginal delivery. Multivariable binary logistic regression analysis and inverse probability of treatment weighting were fitted for statistical analysis.
Unsuspected PAS was reported in one in 3,797 vaginal deliveries. In a multivariable analysis, (i) patient characteristics of older age, (ii) uterine factors such as uterine anomaly and uterine myoma, (iii) pregnancy factors including early-term delivery and prior recurrent pregnancy losses, and (iv) fetal factors of in-utero growth restriction and demise were associated with increased likelihood of encountering unsuspected PAS (all, P<0.05). Of those, uterine anomaly had the greatest association to unsuspected PAS (adjusted-odds ratio [aOR] 6.23, 95% confidence interval [CI] 4.20-9.26). In a propensity score-weighted model, patients in the unsuspected PAS group were more likely to have hemorrhage (65.2% vs 4.1%), blood product transfusion (21.3% vs 0.6%), hysterectomy (14.9% vs <0.1%), coagulopathy (2.9% vs 0.1%), and shock (2.9% vs <0.1%) compared to those without PAS. Patients in the unsuspected PAS group were also more likely to receive manual placental removal compared to those in the non-PAS group (25.1% vs 0.6%).
The current study suggests that although encountering unsuspected PAS among patients undergoing term vaginal delivery is rare, unsuspected PAS is associated with significant morbidity. The observed association between uterine anomalies and PAS warrants further investigation.
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Accepted: November 5, 2022
Received in revised form: October 31, 2022
Received: September 6, 2022
Publication stageIn Press Accepted Manuscript
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