1071 Uterine scars and risk of placenta accreta: is a prior myomectomy equivalent to a C-section?

Abstract

To determine if history of prior myomectomy in those with prior CS increases the risk of placenta accreta spectrum (PAS) disorders. A retrospective cohort study of patients who delivered at a tertiary academic center from 2012-2019 and had a sonographic evaluation of the placenta during their pregnancy at a single ultrasound unit. Demographic, clinical history, sonographic results, and pathology information were collected. Women with a history of C-section and myomectomy were compared based on their number of prior C-sections to those without myomectomy. Analysis was done using Mann-Whitney U test and Chi-square as appropriate. All p-values were considered statistically significant if p <0.05. We identified 585 women with a history of prior C-section (CS) or prior CS with Myomectomy. Of 44 patients in the latter group, 39 (88.6%) had only one prior CS. The baseline characteristics of both groups were similar, except that women with Prior CS with Myomectomy were older (Table 1). The five patients with histologically-confirmed PAS and prior CS with Myomectomy all had one prior CS. Of 33 cases of PAS in the CS only group, 15 (45.4%) occurred in those with multiple prior CS. The rate of PAS in those with one prior CS with Myomectomy was higher compared to those with one prior CS only (12.8% vs. 4.6%; p=0.03), and comparable to those with multiple prior CS (10.3% vs. 12.8%; p=0.65). Of the 33 cases with PAS and CS only, 28 (84.8%) had placenta previa, compared to only 2 of 5 (40%) with PAS in the CS with Myomectomy group (p=.05). The rate of PAS in women with a history of 1 CS and myomectomy was higher compared to those with 1 CS alone, and more comparable to those with multiple prior CS. This suggests an incremental risk associated with myomectomy. As there were too few women with multiple CS with Myomectomy, the incremental risk associated with myomectomy in these women will require larger studies. PAS appears more likely to happen in the absence of placenta previa in those with prior myomectomy.