Adherent Retained Placenta

Adherent retained placenta is a placenta that has not separated from the uterine wall, and remains in place for 30 minutes or more after birth with active management. It results from poor contraction, a partial or complete failure of separation (simple adherence), or abnormal invasion of the myometrium (placenta accreta spectrum). It occurs in about 1 to 2 percent of births, and matters because it causes heavy bleeding, and attempted removal can cause haemorrhage when the placenta is invasive.

• Risk factors: previous caesarean section, previous retained placenta, uterine surgery, placenta praevia, preterm birth, grand multiparity, previous curettage.
• Risk of accreta rises with the number of scars and with praevia.
• Manual removal is done in theatre with antibiotics and anaesthesia.

After birth, the placenta does not deliver with gentle traction, and bleeding may be absent (if no separation) or heavy (partial separation). The uterus is firm or soft depending on blood loss, and the cord does not lengthen.

• No signs of separation (gush of blood, cord lengthening, uterus becoming globular).
• Heavy bleeding with partial separation.
• Differential diagnosis: trapped placenta behind a closed cervix, uterine atony, inversion, placenta accreta spectrum, uterine anomaly.
• Complications: postpartum haemorrhage, shock, infection, uterine inversion from traction, uterine perforation, hysterectomy, maternal death.

The diagnosis is clinical, at 30 minutes after birth, with confirmation in theatre.

• Absence of delivery after 30 minutes with oxytocin and controlled cord traction; vaginal and abdominal examination for the placenta, the uterus and a closed cervix.
• Ultrasound for placental site, accreta signs (loss of the clear zone, lacunae, bladder wall interruption) and retained placenta.
• Pulse, blood pressure, blood loss, haemoglobin, group and cross-match 2 to 4 units.
• Examination under anaesthesia: a plane between placenta and uterine wall shows simple adherence; no plane means accreta.

The principle is manual removal in theatre for a simple adherent placenta, and no forceful removal when there is no plane of separation.

• Supportive: two large-bore cannulae; Ringer's lactate 1 litre; empty the bladder; anaesthesia (spinal or general); consent for hysterectomy; blood available; senior help; avoid repeated cord traction.
• Pharmacological: oxytocin 10 IU IM after birth and 20 IU in 1 litre Ringer's lactate at 125 mL per hour for 4 hours; cefazolin 2 g IV plus metronidazole 500 mg IV before manual removal, then amoxicillin-clavulanate 625 mg oral 8-hourly for 5 days; tranexamic acid 1 g IV over 10 minutes if bleeding exceeds 500 mL; misoprostol 800 micrograms sublingual after removal for atony; carboprost 250 micrograms IM every 15 minutes (maximum 8 doses) if atony persists (not in asthma); ferrous sulphate 200 mg oral 8-hourly for 3 months.
• Procedures: manual removal of the placenta with a hand in the uterus, gently separating the plane with the side of the fingers; inspection of the placenta and cavity; hysterectomy for accreta with heavy bleeding; leaving the placenta in place with delayed management or planned hysterectomy in a referral unit when there is no plane and no bleeding; uterine artery embolisation where available.
• Special groups: suspected accreta spectrum in a woman with a previous caesarean section and placenta praevia needs birth at 34 to 36 weeks in a tertiary unit with 4 to 6 units of blood and a surgical team.
• Red flags: no plane of separation, bleeding above 500 mL, fever above 38 degrees Celsius, shock, uterine inversion.
• Follow-up: observation of bleeding and temperature for 24 hours; ultrasound at 1 week if tissue is left in place; histology review; review at 6 weeks.