Maternal Collapse in Pregnancy and the Puerperium

Definition and Scope

Maternal collapse is an acute event involving the cardiorespiratory and/or central nervous systems resulting in a reduced or absent conscious level (and potentially cardiac arrest and death), at any point in pregnancy and up to 6 weeks postpartum. The incidence of cardiac arrest in pregnancy is around 1 in 36,000 maternities, with a case fatality rate of 42%. Vasovagal attacks and epileptic seizures are the most common causes of maternal collapse overall; major obstetric haemorrhage (~6 in 1000 maternities) is the most common cause of collapse leading to death.

Causes — The "4 H's and 4 T's" Plus Two

A systematic ABCDE approach should be used to identify the cause. The Resuscitation Council (UK) mnemonic covers eight reversible causes, to which two obstetric-specific causes are added:

• 4 H's: Hypoxia; Hypovolaemia; Hypothermia; Hypo-/hyperkalaemia and other electrolyte disturbances
• 4 T's: Thromboembolism; Toxicity (drugs/local anaesthetic); cardiac Tamponade; Tension pneumothorax
• Plus, in pregnancy: Eclampsia; Intracranial haemorrhage

Other important obstetric causes to consider systematically include amniotic fluid embolism (AFE) — incidence 1.7/100,000 maternities, with survival improving from ~14% (1979) to ~81% (2014) — sepsis, and anaphylaxis. Thromboembolism remains the leading cause of direct maternal death in the UK. Where the cause is reversible and identified promptly, survival is markedly improved.

Physiological Considerations in Pregnancy

From 20 weeks' gestation, aortocaval compression by the gravid uterus significantly reduces cardiac output and the efficacy of chest compressions. Reduced lung function, diaphragmatic splinting and increased oxygen consumption mean pregnant women become hypoxic more readily and are harder to ventilate. Difficult intubation and aspiration risk are both increased.

Immediate Management

Resuscitation follows standard Resuscitation Council (UK) ABCDE principles, with modifications for aortocaval compression relief:

• Manual left uterine displacement is effective above 20 weeks (or when the uterus is palpable at/above the umbilicus) and allows effective chest compressions in the supine position.
• Left lateral tilt of 15–30°, head to toe, on a firm surface, is an alternative that still permits effective compressions.
• In major trauma, the spine is protected with a spinal board before any tilt is applied; if no board is available, manual uterine displacement is used instead.
• Supplemental high-flow oxygen is given immediately; bag-and-mask ventilation or a supraglottic airway bridges to intubation, which should be performed immediately by an experienced anaesthetist using a cuffed tube.
• Defibrillation energy levels and Resuscitation Council (UK) algorithm drugs/doses are unchanged from the non-pregnant protocol.
• Two wide-bore cannulae (minimum 16G) are sited early; IV tranexamic acid significantly reduces mortality from postpartum haemorrhage.

Perimortem Caesarean Section (PMCS)

In women over 20 weeks' gestation, if there is no response to correctly performed CPR within 4 minutes of collapse — or resuscitation continues beyond this — PMCS should be undertaken to aid maternal resuscitation, ideally achieved within 5 minutes of collapse. PMCS must not be delayed by moving the woman; it is performed on the spot, using whichever incision (midline vertical or suprapubic transverse) gives fastest access. A scalpel and cord clamps should be immediately available on the resuscitation trolley in any area where collapse may occur.

High-Yield Exam Points

• 4 H's + 4 T's + eclampsia + intracranial haemorrhage = the systematic differential for maternal collapse.
• Aortocaval compression is significant from 20 weeks; relieve with manual left uterine displacement (preferred for effective compressions) or 15–30° left lateral tilt.
• PMCS trigger: no ROSC within 4 minutes of CPR (>20 weeks gestation); target delivery by 5 minutes — perform where the collapse occurred, do not move the patient.
• Defibrillation energy and ACLS drug doses are unchanged in pregnancy.
• IV tranexamic acid (Grade A evidence) reduces PPH-related mortality.
• Team call-out for maternal collapse: senior midwife + obstetrician + obstetric anaesthetist added to the standard arrest team; neonatal team called early if antepartum collapse ≥22+0 weeks.
• All cases of maternal collapse require an incident form; maternal deaths are reported to MBRRACE-UK.

Source: RCOG Green-top Guideline No. 56 (Second edition published December 2019 (Chu J, Johnston TA, Geoghegan J. BJOG 2020;127:e14–e52). Reviewed by the RCOG Guidelines Committee in December 2024, who agreed to extend the guideline for two years; the next full review is due to commence in 2026. The first edition was published in 2011.)

Read the original on rcog.org.uk

Clinically reviewed by NHS obstetricians and gynaecologists · Source last updated Second edition published December 2019 (Chu J, Johnston TA, Geoghegan J. BJOG 2020;127:e14–e52). Reviewed by the RCOG Guidelines Committee in December 2024, who agreed to extend the guideline for two years; the next full review is due to commence in 2026. The first edition was published in 2011.

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