Focal-Occult Placenta Accreta Spectrum: A Clandestine Source of Maternal Morbidity

INTRODUCTION: While focal-occult placenta accreta spectrum (PAS) is known to lead to adverse outcomes, little is known of the morbidity in comparison to previa-associated PAS. METHODS: After IRB approval, retrospective review was conducted of pathologically confirmed (decidual layer absence or basal-plate myometrial fibers) PAS from 2018 to 2021 at a tertiary care center. Baseline characteristics and surgical, obstetric, and subsequent pregnancy outcomes were recorded. Focal-occult PAS was compared with previa-associated PAS using Kruskal-Wallis/Chi-square tests; P <.05 was considered significant. RESULTS: A total of 56 cases were identified: 22 previa-associated and 34 focal-occult PAS. All patients with previa-associated and 26.5% of those with focal-occult PAS underwent hysterectomy. Of the previa-associated PAS patients, 20 of 22 were diagnosed antenatally, as was 1 of 34 focal-occult PAS patients. Mean maternal age (32.5 vs. 33.1 year), number of previous dilation and curettage procedures (0.4 vs. 0.3), and in vitro fertilization rates (4.5% vs. 23.5%) were not significantly different between groups. Mean parity (3.7 vs. 1.4), gestational age at delivery (34.3 vs. 35.7 weeks), any previous cesarean delivery (95.5% vs. 29.4%), mean number of previous cesareans (2.5 vs. 0.5), and placental locations were significantly different between groups. All measures of morbidity, including postpartum hemorrhage rates (81.0% vs. 75.8%), median qualitative blood loss (1,500cc, range: 500–9,516cc vs. 1,660cc, range: 350–12,220cc), mean units of red blood cells transfused (1.8 vs. 1.9), massive transfusion (9.1% vs. 20.6%), ICU admission (9.1% vs. 14.7%), and reoperation rates (9.1% vs. 32.4%) were similar between groups. Six focal-occult PAS patients had a subsequent pregnancy, and two had recurrent PAS. CONCLUSION: Despite representing lower grade PAS, focal-occult PAS has similar measures of morbidity when compared to previa-associated PAS, potentially attributable to lack of antenatal detection.