Objective: In a 2015 Maternal-Fetal Medicine Units Network study, only half of placenta accreta spectrum cases were suspected before delivery, and the outcomes in the anticipated cases were paradoxically poorer than in unanticipated placenta accreta spectrum cases. This was possibly because the antenatally suspected cases were of greater severity. We sought to compare the outcomes of expected vs unexpected placenta accreta spectrum in a single large US center with multidisciplinary management protocol.

Study design: This was a retrospective cohort study carried out between Jan. 1, 2011, and June 30, 2018, of all histology-proven placenta accreta spectrum deliveries in an academic referral center. Patients diagnosed at the time of delivery were cases (unexpected placenta accreta spectrum), and those who were antentally diagnosed were controls (expected placenta accreta spectrume). The primary and secondary outcomes were the estimated blood loss and the number of red blood cell units transfused, respectively. Variables are reported as median and interquartile range or number (percentage). Analyses were made using appropriate parametric and nonparametric tests.

Results: Fifty-four of the 243 patients (22.2%) were in the unexpected placenta accreta spectrum group. Patients in the expected placenta accreta spectrum group had a higher rate of previous cesarean delivery (170 of 189 [89.9%] vs 35 of 54 [64.8%]; P < .001) and placenta previa (135 [74.6%] vs 19 [37.3%]; P < .001). There was a higher proportion of increta/percreta in expected placenta accreta spectrum vs unexpected placenta accreta spectrum (125 [66.1%] vs 9 [16.7%], P < .001). Both primary outcomes were higher in the unexpected placenta accreta spectrum group (estimated blood loss, 2.4 L [1.4-3] vs 1.7 L [1.2-3], P = .04; red blood cell units, 4 [1-6] vs 2 [0-5], P = .03).

Conclusion: Our data contradict the Maternal-Fetal Medicine Units results and instead show better outcomes in the expected placenta accreta spectrum group, despite a high proportion of women with more severe placental invasion. We attribute this to our multidisciplinary approach and ongoing process improvement in the management of expected cases. The presence of an experienced team appears to be a more important determinant of maternal morbidity in placenta accreta spectrum than the depth of placental invasion.