Perimortem Caesarean and Maternal Cardiac Arrest
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Direct answer
Perimortem caesarean is an emergency delivery of the fetus performed during maternal cardiac arrest, to relieve aortocaval compression and improve the chance of fetal survival. The four-minute rule sets the target, so the operation should begin within about four minutes of arrest while cardiopulmonary resuscitation continues. Maternal resuscitation continues throughout, with the obstetric and resuscitation teams working in parallel.
What you must remember
- Trigger: Cardiac arrest in a pregnant woman at or beyond about 20 weeks, when the enlarged uterus compresses the inferior vena cava and aorta.
- Left uterine displacement: A manual or wedge tilt of the uterus to the left during CPR relieves aortocaval compression and improves venous return.
- Four-minute rule: Delivery aims to begin within about four minutes of arrest and be completed by about five minutes, because fetal survival falls as the interval lengthens.
- Procedure: A rapid midline incision and delivery, with the neonatal team ready and the anaesthetist continuing CPR.
- Causes: Haemorrhage, amniotic fluid embolism, pulmonary embolism, eclampsia, sepsis, anaphylaxis, local anaesthetic toxicity and magnesium toxicity.
- Magnesium toxicity: Calcium gluconate is the antidote, and the magnesium sulphate infusion is stopped immediately.
- Defibrillation: Shocks for ventricular fibrillation or pulseless ventricular tachycardia follow standard protocols, with no pregnancy-specific change in energy.
A stepwise resuscitation pathway
A woman at 32 weeks collapses on the labour ward and is pulseless. The steps below run in parallel, with the obstetric and resuscitation teams working together.
- Start CPR and call for help: Recognise the arrest, activate the emergency team, and start chest compressions and ventilation without delay.
- Displace the uterus to the left: Tilt the uterus manually or with a wedge throughout resuscitation to relieve aortocaval compression.
- Treat reversible causes: Check for haemorrhage, embolism, eclampsia, sepsis, anaphylaxis, local anaesthetic toxicity and magnesium toxicity.
- Decide on perimortem caesarean: If circulation has not returned by about four minutes, the obstetrician begins delivery while CPR continues.
- Deliver rapidly: Make a vertical midline incision, deliver the baby to the neonatal team, and then control uterine bleeding.
- Continue maternal care: Manage shock and post-arrest care, with ICU admission and neurological monitoring as needed.
Resuscitation is modified for pregnancy, with early airway control because aspiration and rapid desaturation are common.
Where the exam tries to catch you
Viva and MCQ vignettes usually test the timing and the displacement step.
- Trap: Delaying the caesarean until the mother has been resuscitated. Correct: The four-minute target means the delivery decision starts early, in parallel with CPR.
- Trap: Using the standard supine CPR position in late pregnancy. Correct: Left uterine displacement is needed because the gravid uterus compresses the great vessels.
- Trap: Ignoring magnesium toxicity in a woman on magnesium sulphate. Correct: Calcium gluconate is the antidote, and the infusion is stopped at once.
Frequently asked questions
What is the four-minute rule in perimortem caesarean?
The four-minute rule states that perimortem caesarean should begin within about four minutes of maternal cardiac arrest, to give the best chance of fetal survival. The target is a guide, and the decision is made in parallel with resuscitation.
Why is the uterus displaced to the left during maternal cardiac arrest?
Left uterine displacement relieves compression of the inferior vena cava and aorta by the gravid uterus, which improves venous return. It is performed manually or with a wedge during CPR.
From what gestation is perimortem caesarean considered?
Perimortem caesarean is generally considered from around 20 weeks, when the uterus is large enough to compress the great vessels. Fetal survival becomes more realistic after about 24 weeks.
Which drug toxicity can cause cardiac arrest in a woman on magnesium sulphate?
Magnesium toxicity can cause cardiac arrest in a woman on magnesium sulphate, typically after excessive dosing or in renal impairment. Calcium gluconate is the antidote, and the magnesium infusion is stopped immediately.
What is the purpose of a maternal near-miss review after a cardiac arrest?
A maternal near-miss review analyses a life-threatening event to identify delays and gaps in care. In India, MoHFW operational guidelines for near-miss review sit alongside Maternal Death Surveillance and Response, so that system-level lessons can be acted on.