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A retained placenta has failed to separate, has separated but become trapped, or is abnormally attached. It can cause postpartum haemorrhage and infection; treatment combines timely assessment, control of bleeding and safe removal, with a different strategy when placenta accreta spectrum is suspected.
After the fetus is born, contraction and retraction of the myometrium reduce the area of the placental bed. The placenta cannot shrink with it and normally separates through the maternal decidua. Continued contraction compresses the maternal vessels crossing the myometrium, providing an important mechanism of haemostasis. A fragment left attached can both expose bleeding vessels and interfere with effective contraction.
Three mechanisms organise the causes:
- Failure of separation, often associated with uterine atony. Exhaustion after prolonged labour, overdistension of the uterus and a full urinary bladder may impair effective contraction or expulsion. A detached placenta can also remain in a poorly contracting uterus.
- Entrapment after separation behind a closing cervix or constricted lower portion of the uterus. Nineteenth-century texts discussed “hour-glass contraction”, but the diagnosis was contested even then; not every trapped placenta proves that an hourglass-shaped partition has formed in the body of the uterus.
- Abnormal attachment, now classified within placenta accreta spectrum. Deficiency of the normal decidua at the attachment site allows abnormal adherence to, or invasion of, the myometrium. Previous uterine surgery is an important risk factor. A succenturiate placental lobe or fragment can also remain after the main placenta has been delivered, so an apparently expelled organ does not exclude retained tissue.
Consequences include immediate or delayed postpartum haemorrhage, hypovolaemic shock, anaemia, endometritis and sepsis. Retained fragments may delay normal shrinking of the uterus. Forceful pulling on the umbilical cord adds the risks of cord rupture and uterine inversion. Conversely, indiscriminate delay while bleeding continues can be fatal.
An 1867 answer would assess bleeding, the size and contraction of the uterus, whether separation had occurred and whether the outlet was obstructed. Emptying the urinary bladder, encouraging effective contraction and supporting the uterus were rational preliminary principles. If the placenta remained attached or trapped and the circumstances demanded intervention, manual removal with external support of the uterus was the principal operative resource. The historical difficulty was to distinguish a removable attachment from a dangerously adherent one. A September 1867 report describes an apparent “hour-glass” retention actually relieved by loosening a tight abdominal binder; it is useful evidence for examining the mechanism rather than trusting the diagnostic label.[ref]
Hour-glass contraction of the uterus simulated by the pressure of a narrow binder by William T. Greene (1867). British Medical Journal, 7 September 1867, p. 206: retained placenta after external constriction, followed by expulsion when the binder was loosened
The case is an observation, not proof that all retention has an external cause.Current care monitors blood loss and maternal condition, secures intravenous access and obtains skilled obstetric help. With active third-stage management, failure to complete the third stage of labour by 30 minutes is prolonged; with physiological management, the cited NICE threshold is 60 minutes. These thresholds do not justify waiting through active haemorrhage or instability. A trained clinician may use controlled cord traction with uterine counterpressure under appropriate conditions; unopposed pulling is not the same technique.[ref]
Intrapartum care by NICE. NG235, recommendations 1.10.20–1.10.28: prolonged third stage, intravenous access, uterotonics and anaesthesia for removal
When removal is required, examination and manual removal take place with appropriate anaesthesia, aseptic technique, external support and readiness to manage haemorrhage. The placenta and membranes are checked for completeness; persistent bleeding prompts assessment for retained fragments, uterine atony, trauma and disordered clotting. Antibiotic prophylaxis accompanies manual removal. Give uterotonics for associated postpartum haemorrhage and to maintain contraction after removal, rather than repeatedly giving them as a substitute for removing a retained organ in a non-bleeding patient. WHO's 2025 recommendations advise preparing for manual removal after 30 minutes if the placenta remains undelivered and distinguish this decision from treatment of established postpartum haemorrhage.[ref]
Consolidated guidelines for the prevention, diagnosis and treatment of postpartum haemorrhage by the World Health Organization (2025). Recommendations 30–31: uterotonics for retained placenta in the presence of haemorrhage, preparation for removal, and routine antibiotic prophylaxis
If no safe separation plane exists and placenta accreta spectrum is suspected, repeated forceful attempts to peel off the placenta can precipitate catastrophic haemorrhage. Escalate to an experienced multidisciplinary team and a haemorrhage plan. Definitive surgery, including hysterectomy, may be necessary; selected conservative management leaving the placenta in place requires specialist selection and follow-up. Current guidance explicitly advises avoiding attempted separation in women with a high probability of placenta accreta spectrum.[ref]
Placenta Praevia and Placenta Accreta Spectrum: Diagnosis and Management by the Royal College of Obstetricians and Gynaecologists (2026). Key recommendations on avoiding placental separation, specialist multidisciplinary care and follow-up when the placenta is left in situ
Thus the word “retained” identifies an urgent clinical problem, but the cause determines whether ordinary manual separation is safe.