Key Facts

Retained placenta is a significant cause of postpartum haemorrhage and occurs when the placenta fails to separate or be delivered within the expected timeframe after birth of the baby.

Epidemiology

• Incidence: approximately 1-3% of vaginal deliveries
• Higher incidence with preterm delivery and in certain populations
• Accounts for significant proportion of PPH requiring intervention

Aetiology

• Placenta adherens: most common; placenta has separated but is retained due to inadequate uterine contraction or a closed cervix
• Trapped placenta: placenta has separated but is trapped behind a closing cervix
• Placenta accreta spectrum: abnormal placental invasion into the myometrium preventing normal separation

Pathophysiology

• Normal third stage: uterine contractions reduce placental bed area, causing shearing and placental separation at the decidua spongiosa layer
• Retained placenta occurs when this process fails due to: inadequate contraction (atony), cervical spasm (trapping separated placenta), or abnormal implantation (accreta)
• Risk of haemorrhage increases with time as the uterus cannot fully contract around the bleeding placental site

Typical Presentation

• Placenta not delivered within expected timeframe (30 min with active management)
• Cord signs of separation may or may not be present (cord lengthening, small gush of blood, uterus becomes firmer and rises)
• Ongoing vaginal bleeding
• Cord may snap during controlled cord traction

Red Flags

• Heavy ongoing vaginal bleeding
• Signs of hypovolaemia (tachycardia, hypotension)
• Signs of uterine inversion (if excessive traction applied)
• Difficulty during manual removal (suggests accreta)
• Signs of infection (if prolonged retention)

Bedside

• Assess vital signs (blood loss estimation)
• Palpate uterus (assess contraction and fundal height)
• Examine any delivered placental tissue for completeness
• IV access (two large-bore cannulae)

Bloods

• FBC
• Group and save / crossmatch
• Coagulation screen

Imaging

• Ultrasound: may help distinguish type of retained placenta and guide management
• Doppler USS: useful if accreta suspected

Special Tests

• None routinely required; histological examination of placenta after removal

Non-pharmacological

• Ensure empty bladder (catheterise)
• Attempt breastfeeding (endogenous oxytocin release)
• Controlled cord traction (do not pull excessively - risk of uterine inversion)
• If haemorrhage: ABCDE approach, resuscitation

Pharmacological

• Oxytocin 20 IU in 20 mL saline via umbilical vein injection (Pipingas technique): may promote separation
• IV oxytocin infusion (40 IU in 500 mL over 4 hours)
• Glyceryl trinitrate (GTN) sublingual 400-800mcg may relax cervical spasm (limited evidence)

Surgical/Interventional

• Manual removal of placenta (MROP): performed in theatre under regional (spinal/epidural top-up) or general anaesthesia
• Technique: hand inserted into uterus, fingers used to separate placenta from uterine wall in the cleavage plane
• Prophylactic antibiotics at time of MROP (e.g., co-amoxiclav 1.2g IV)
• If accreta suspected and placenta cannot be separated: do not force - may require hysterectomy or conservative management (leaving placenta in situ with methotrexate - specialist centres only)
• Active management of third stage after MROP (oxytocin, uterine massage)

Referral Criteria

• Consultant obstetrician involvement for all MROP
• Anaesthetic team for theatre
• Blood bank alert for potential major haemorrhage
• If accreta diagnosed: refer to specialist centre

• MROP successful in majority of cases (>95% for adherens/trapped placenta)
• PPH at time of retained placenta: ~40%
• Recurrence risk in subsequent pregnancies: 8-15%
• Placenta accreta: if unsuspected, can cause massive haemorrhage requiring hysterectomy
• Endometritis risk increased after MROP (5-10%)
• Long-term fertility generally unaffected
• If conservative management of accreta: resolution over weeks-months with risk of infection, haemorrhage, and need for delayed hysterectomy

Types of Retained Placenta