Clinical significance of retained products of conception in placenta previa: a retrospective analysis

Abstract

Background: Retained products of conception (RPOC) often cause severe postpartum hemorrhage (PPH) but the clinical significance of RPOC in placenta previa is unclear. This study aimed to investigate the clinical significance of RPOC in women with placenta previa. The primary outcome was to evaluate risk factors of RPOC and the secondary outcome was to consider risk factors of severe PPH.

Methods: Singleton pregnant women with placenta previa who underwent cesarean section (CS) and placenta removal during the operation at the National Defense Medical College Hospital between January 2004 and December 2021 were identified. A retrospective analysis was performed to examine the frequency and risk factors of RPOC and the association of RPOC with severe PPH in pregnant women with placenta previa.

Results: This study included 335 pregnant women. Among these, 24 (7.2%) pregnant women developed RPOC. Pregnant women with prior CS (Odds Ratio (OR) 5.98; 95% Confidence Interval (CI) 2.35-15.20, p < 0.01), major previa (OR 3.15; 95% CI 1.19-8.32, p < 0.01), and placenta accreta spectrum (PAS) (OR 92.7; 95% CI 18.39-467.22, p < 0.01) were more frequent in the RPOC group. Multivariate analysis revealed that prior CS (OR 10.70; 95% CI 3.47-33.00, p < 0.01,) and PAS (OR 140.32; 95% CI 23.84-825.79, p < 0.01) were risk factors for RPOC. In pregnant women who have placenta previa with RPOC or without RPOC, the ratio of severe PPH were 58.3% and 4.5%, respectively (p < 0.01). Furthermore, the occurrence of prior CS (OR 9.23; 95% CI 4.02-21.20, p < 0.01), major previa (OR 11.35; 95% CI 3.35-38.38, p < 0.01), placenta at the anterior wall (OR 3.44; 95% CI 1.40-8.44, p = 0.01), PAS (OR 16.47; 95% CI 4.66-58.26, p < 0.01), and RPOC (OR 29.70; 95% CI 11.23-78.55, p < 0.01) was more in pregnant women with severe PPH. In the multivariate analysis for severe PPH, prior CS (OR 4.71; 95% CI 1.29-17.13, p = 0.02), major previa (OR 7.50; 95% CI 1.98-28.43, p < 0.01), and RPOC (OR 13.26; 95% CI 3.61-48.63, p < 0.01) were identified as risk factors.

Conclusions: Prior CS and PAS were identified as risk factors for RPOC in placenta previa and RPOC is closely associated with severe PPH. Therefore, a new strategy for RPOC in placenta previa is needed.

Keywords: Placenta accrete spectrum; Placenta previa; Postpartum hemorrhage; Retained products of conception.

Fig. 1

These images were diagnosed for retained products of conception (RPOC) in pregnant patients with placenta previa after operation. RPOC was represented as an echogenic mass at transvaginal color Doppler ultrasonography (US) after one day of operation (a), which was detected no flow, a heterogenous signal area at T1-weighted magnetic resonance imaging (MRI) (b), and a high signal area at T2-weighted MRI (c) and contrase-enhanced T1-weighted MRI (d) (red arrow heads show)

Fig. 2

The pathological images of placenta accreta spectrum (PAS) in a pregnant patient with placenta previa. These images expressed a pathological feature of PAS; findings of invasion of trophoblastic tissue into the myometrium (red arrow heads show) and fibrin deposition in in some areas (blue arrow heads show). (a × 40, (b) × 100))

Fig. 3

A study flow chart in pregnant patients with placenta previa. All patients with placenta previa were performed cesarean section (CS) (*). Retained products of conceptions (RPOC) (**) was diagnosed using ultrasonography (US), contrast-enhanced computed tomography (CT), and contrast-enhanced magnetic resonance imaging (MRI) according to previous reports until seven days after CS. Severe postpartum hemorrhage (severe PPH) (***) was defined as > 1000 ml of blood loss within 24 h of CS