Trapped Placenta

Trapped placenta is a placenta that has separated from the uterine wall but cannot be delivered because the cervix has closed, or a constriction ring has formed above it. It results from delay in delivery of the placenta, early administration of ergometrine or misoprostol before the placenta delivers, or premature cord traction. It occurs in less than 1 percent of births, and matters because blood collects behind the placenta, causing heavy bleeding and infection.

• Risk factors: delay in delivering the placenta, uterotonic drug given before the placenta, previous cervical surgery, uterine anomaly, preterm birth.
• Placenta is separated but trapped, unlike an adherent placenta.
• Relaxing the cervix usually allows delivery.

After birth, the placenta can be felt in the lower segment or vagina but does not deliver, with a closed or narrow cervix and a uterus that is firm and globular. Bleeding is variable and the woman has lower abdominal pain.

• Hour glass shaped uterus with a ring across the lower segment.
• Cord lengthened but placenta stuck at the cervix.
• Differential diagnosis: adherent placenta, placenta accreta, uterine inversion, atony with retained clots, uterine anomaly.
• Complications: postpartum haemorrhage, shock, infection, uterine inversion from traction, manual removal under anaesthesia, hysterectomy.

The diagnosis is made on examination, with confirmation of separation.

• Abdominal palpation for a firm uterus with a constriction ring; vaginal examination for a placenta in the lower segment or cervix.
• Ultrasound: placenta in the lower segment with a thin cervical rim and no accreta signs.
• Pulse, blood pressure, blood loss; haemoglobin; group and cross-match 2 units.
• Check that the cervix has not formed a tight ring and that no inversion is present.

The principle is to relax the uterus and cervix, empty the bladder, and then deliver the placenta with gentle traction, with manual removal under anaesthesia if needed.

• Supportive: call for help; two cannulae; Ringer's lactate 1 litre; empty the bladder by catheter; lie flat with a warm room; avoid forceful cord traction; consent for manual removal.
• Pharmacological: glyceryl trinitrate 400 to 800 micrograms sublingual (or 50 to 200 micrograms IV bolus, titrated) for uterine and cervical relaxation, held if systolic pressure is below 100 mmHg; terbutaline 0.25 mg subcutaneous once as an alternative; spinal anaesthesia or general anaesthesia with sevoflurane for manual removal; cefazolin 2 g IV plus metronidazole 500 mg IV before manual removal; oxytocin 10 IU IM and 20 IU in 1 litre Ringer's lactate at 125 mL per hour for 4 hours after delivery of the placenta; tranexamic acid 1 g IV over 10 minutes if bleeding exceeds 500 mL.
• Procedures: gentle controlled cord traction after relaxation; manual removal of the placenta under anaesthesia (gently dilate the cervix with the fingers, cup the placenta and withdraw it); inspection of the placenta and cavity; balloon tamponade for oozing.
• Special groups: women with tachyarrhythmia or heart disease use glyceryl trinitrate rather than terbutaline; hypotensive women avoid glyceryl trinitrate and use terbutaline.
• Red flags: heavy bleeding, shock, no relaxation of the cervix, fever above 38 degrees Celsius, uterine inversion.
• Follow-up: observation of bleeding and temperature for 24 hours; haemoglobin at 24 hours; review at 6 weeks; plan the next birth with early oxytocin and no ergometrine before the placenta.