Risk factors for partial placental retention after <scp>Cesarean</scp> delivery: a preliminary report

OBJECTIVE: To identify risk factors for partial placental retention (PPR) after Cesarean delivery (CD). METHODS: This was a retrospective case-control study of patients with suspected complications after CD, including 25 cases of PPR and 75 controls without evidence of PPR. The diagnosis of PPR was made using high-resolution ultrasound and was confirmed histologically in all cases. To identify potential risk factors for PPR, we compared demographic and clinical data between cases of PPR and controls. RESULTS: Mode of conception, congenital uterine anomaly (CUA) and clinical indication for postpartum ultrasound assessment were all significantly associated with PPR after CD on univariable analysis. Patients with PPR were more likely to have conceived using assisted reproductive technology (9/22 (40.9%) vs 13/75 (17.3%); odds ratio (OR), 3.30 (95% CI, 1.17-9.33); P = 0.02), have a CUA (3/25 (12.0%) vs 1/75 (1.3%); OR, 10.1 (95% CI, 1.00-101.93); P = 0.05), and present with prolonged postpartum bleeding as the main indication for ultrasound assessment (20/25 (80.0%) vs 25/75 (33.3%)) as compared to acute bleeding (3/25 (12.0%) vs 7/75 (9.3%); OR, 0.54 (95% CI, 0.12-2.34)) or other indications (2/25 (8.0%) vs 43/75 (57.3%); OR, 0.06 (95% CI, 0.01-0.27)) (P < 0.001). Both indication for ultrasound assessment and presence of a CUA were retained in the multivariable analysis. In 19/20 (95.0%) cases with PPR for which data on placental location were available, the placenta was located in the upper uterine cavity antenatally, and none of the patients with PPR had antenatal ultrasound signs suggestive of a high probability of placenta accreta spectrum at birth. In all cases of PPR, the retained placental tissue was removed entirely using polyp or ovum forceps under ultrasound guidance, indicating that the placenta was not abnormally attached to the myometrium. CONCLUSIONS: Patients with a known CUA should be advised that they are at higher risk of PPR, and the obstetric team should take measures to minimize this risk. Prolonged postpartum bleeding is predictive of PPR after CD, and patients experiencing this should be referred for ultrasound assessment without delay. PPR after CD is not diagnostic of placenta accreta spectrum and surgical evacuation of the uterus is unlikely to be complicated. © 2026 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.