Focal-occult placenta accreta: a clandestine source of maternal morbidity.

Background: Focal-occult placenta accreta spectrum is known to cause adverse obstetrical morbidity outcomes, however, direct comparisons with previa-associated placenta accreta spectrum morbidity are lacking.

Objective: We sought to compare the baseline characteristics, surgical and obstetrical morbidity, and subsequent pregnancy outcomes of patients with focal-occult placenta accreta spectrum with those of patients with previa-associated accreta.

Study Design: A retrospective review was conducted of all pathologically confirmed placenta accreta spectrum cases from 2018 to 2022 at a tertiary care center. The baseline characteristics, surgical, obstetrical, and subsequent pregnancy outcomes were recorded. Cases of focal-occult placenta accreta spectrum was compared with cases of previa-associated placenta accreta spectrum across a range of morbidity characteristics including hemorrhagic factors, interventions, postdelivery reoperations, infections, and intensive care unit admission. Statistical comparison was performed using Kruskal-Wallis or chi-square tests, and a P value of <.05 was considered significant.

Results: A total of 74 cases were identified with 43 focal-occult and 31 previa-associated placenta accreta spectrum cases. Of those, 25.6% of the patients with focal-occult placenta accreta spectrum and 100% of the patients with previa-associated placenta accreta spectrum underwent a hysterectomy. One case of focal-occult placenta accreta spectrum and 29 cases of previa-associated placenta accreta spectrum were diagnosed antenatally. Patients with focal-occult placenta accreta spectrum did not differ from those with previa-associated placenta accreta spectrum in mean maternal age (33.0 vs 33.1 years), body mass index, or the incidence of previous dilation and curettage procedures (16.3% vs 25.8%). Patients with focal-occult placenta accreta spectrum were significantly more likely to have a lower mean parity (1.5 vs 3.6 gestations), higher gestational age at delivery (36.1 vs 33.9 weeks' gestation), and were less likely to have had a previous cesarean delivery (12/43, 27.9% vs 30/31, 96.8%). In addition, patients with focal-occult placenta accreta spectrum had less previous cesarean deliveries (mean, 0.5 vs 2.3), were more likely to have undergone in vitro fertilization (20.9% vs 3.2%), and less likely to have anterior placentation. When contrasting the clinical outcomes of patients with focal-occult placenta accreta spectrum with those with previa-associated placenta accreta spectrum, the postpartum hemorrhage rates (71.0% vs 67.4%), mean quantitative blood loss (2099 mL; range, 500-9516 mL vs 2119 mL; range 350-12,220 mL), mean units of red blood cells transfused (1.4 vs 1.7), massive transfusion rate (9.3% vs 3.2%), and intensive care unit admission rates (11.6% vs 6.5%) were not significantly different, but there was a nonsignificant trend toward higher morbidity among patients with focal-occult accreta. Patients with focal-occult accreta had a higher incidence of reoperations or return to the operating room (30.2 vs 6.5%; P=.01). When comparing focal-occult with previa-associated placenta accreta spectrum, the composite outcomes, including hemorrhagic morbidity (77.4% vs 74.4%), any maternal morbidity (83.9% vs 76.7%), and severe maternal morbidity (64.5% vs 65.1%), were not significantly different between the groups. Nine focal-occult placenta accreta spectrum patients had a subsequent pregnancy, and 3 of those had recurrent placenta accreta spectrum.

Conclusion: Focal-occult placenta accreta spectrum presents with fewer identifiable risk factors than placenta previa-associated placenta accreta spectrum but may be associated with an in vitro fertilization pregnancy. Patients with focal-occult placenta accreta spectrum was observed to have a higher incidence of reoperation when compared with patients previa-associated placenta accreta spectrum, and no other statistically significant differences in morbidity outcomes were observed. The absence of differences in morbidity outcomes may be attributable to a lack of antenatal detection of focal-occult accreta and merits further investigation.