Maternal Collapse: Causes, CPR in Pregnancy, Resuscitative Hysterotomy & Shock

Maternal collapse and shock in one place: what causes it, how CPR changes in pregnancy, when to do a resuscitative hysterotomy, and how to recognise and treat shock. Based on the OLSS (Obstetric Life Saving Skills) lectures on maternal collapse and maternal shock at Hospital Sultan Haji Ahmad Shah (HOSHAS), Temerloh.

Definition and why it is harder in pregnancy

Maternal collapse is any acute event involving the cardiorespiratory system and/or a reduced or absent conscious level, at any stage of pregnancy up to 6 weeks postpartum. It is rare but life-threatening, and the outcome for the mother (and the fetus) depends on prompt and effective resuscitation.

Resuscitating a pregnant woman is harder because:

• Intubation and ventilation are difficult: larger breasts and higher chest wall resistance, plus pharyngeal and nasal oedema.
• Blood loss can be rapid because of the increased cardiac output and hyperdynamic circulation.
• Hypoxia is more severe: the diaphragm is splinted and oxygen consumption is higher.
• Aortocaval compression by the gravid uterus can reduce cardiac output by 30-40%, making CPR ineffective unless the uterus is moved off the great vessels.

Causes

The lecture groups the causes A to H:

Reversible causes: 4Hs, 4Ts and E

Approach: DRS ABCD

Rapid assessment and action, with the maternal modifications (left uterine displacement or left lateral tilt) added from the start.

D: Danger

Quickly assess the situation, check for danger and make the area safe.

R: Response

Check for a response with COWS: Can you hear me? Open your eyes. What is your name? Squeeze my hand. No response: shout for help.

S: Shout for help

Call 999 (MERS 999) outside hospital, or activate the hospital's Code Red / Red Alert.

A: Airway

• Open the airway and keep it open.
• Oropharyngeal airway (OPA): choose the size by measuring from the corner of the mouth to the angle of the jaw.
• Laryngeal mask airway (LMA): preferred sizes 4 and 5.
• Intubate early if a skilled provider is available.

B: Breathing

• Look for chest rise and abdominal movement, listen for breathing and abnormal sounds, feel for expired air.
• Breathing normally: put her in the recovery position and keep monitoring.
• Not breathing: start CPR.
• Rescue breaths with a bag-valve-mask: seal the mask over the nose and mouth with the head tilted, and give 1 breath every 5-6 seconds; check the pulse every 2 minutes.

C: Circulation (CPR)

Continue compressions until a pulse returns, another responder takes over, or you are exhausted.

D: Defibrillation

Attach a defibrillator (AED) as soon as one arrives. Shockable rhythms are pulseless VT and VF. Biphasic: first shock 120-200 J.

In the advanced life support algorithm for pregnancy, the rhythm is analysed every 2 minutes:

• PEA / asystole: resume compressions; adrenaline (epinephrine) IV/IO every 3-5 minutes.
• Pulseless VT / VF: defibrillate, resume compressions; adrenaline IV/IO every 3-5 minutes, and IV amiodarone 300 mg after the 2nd shock.
• Remove fetal monitors if present, and assess the gestational age.

Remark: OPA = oropharyngeal airway; LMA = laryngeal mask airway; AED = automated external defibrillator; VT = ventricular tachycardia; VF = ventricular fibrillation; PEA = pulseless electrical activity; IO = intraosseous.

Maternal modifications

The gravid uterus compresses the aorta and inferior vena cava, so cardiac output falls and CPR becomes ineffective. Two ways round it:

1. Left uterine displacement (LUD), done manually and continuously: the pull technique is preferred (one or two hands), or the push technique.
2. Left lateral tilt of 15-30 degrees, using a wedge or by tilting the operating table.

Resuscitative hysterotomy (perimortem caesarean)

Perform it within 4 minutes of collapse.

• Indication: cardiac arrest in pregnancy at a gestation >20 weeks, or with the fundus at or above the umbilicus. The purpose is to save the mother.
• Primary rationale: increases the chance of maternal return of spontaneous circulation, improving maternal cardiac output by about 25% by reducing uterine blood flow and relieving diaphragmatic pressure and aortocaval compression.
• Secondary rationale: it may save a viable fetus.
• Where: at the site of maternal resuscitation. Do not delay to transfer to the OT. Informed consent is not necessary.

Equipment

Team allocation: one team continues maternal resuscitation (normal ALS, lateral uterine displacement, early intubation), one prepares and performs the hysterotomy, and one prepares for neonatal resuscitation.

Steps

1. Get into the abdomen: pour antiseptic on the abdomen (draping is unnecessary) and use the incision that gives the most rapid access, midline or suprapubic transverse.
2. Get into the uterus: classical (vertical) caesarean incision; cut through the placenta if necessary.
3. Get the baby out: deliver the head or breech, with fundal pressure to assist.
4. Cord and placenta: clamp and cut the cord and hand the baby to the neonatal team. Third stage by MRP / CCT; give IM oxytocin 10 IU and intramyometrial carboprost 250 mcg.
5. Close the abdomen: single-layer uterine closure, simple rectus closure, continuous skin closure.
6. Post-resuscitative care: broad-spectrum antibiotics, check for bleeding once the circulation is restored, and intensive care monitoring.

Remark: OT = operating theatre; ALS = advanced life support; MRP = manual removal of placenta; CCT = controlled cord traction; IM = intramuscular.

Post-event management

• Manage complications.
• Incident reporting.
• Documentation and team debriefing. Record the persons involved, the time of the event, the procedures performed and the drugs given, plus the resuscitation process and the counselling and debriefing.
• Training and drills.

Shock in pregnancy

Shock is inadequate tissue perfusion, leading to cellular hypoxia and multi-organ dysfunction. Early recognition and treatment are crucial. The commonest obstetric cause is hypovolaemic shock from postpartum haemorrhage.

Types of shock

1. Hypovolaemic
2. Septic
3. Cardiogenic
4. Neurogenic
5. Amniotic fluid embolism
6. Anaphylactic

Physiological changes that mask shock

Oedema is common because of increased capillary hydrostatic pressure and decreased colloid oncotic pressure.

Clinical features by blood loss

Assessing a mother in shock

• General: colour (pale or cyanotic), peripheries (cold and clammy).
• Respiratory: rising respiratory rate.
• Renal: urine output <0.5 mL/kg/h.
• CNS: AVPU (alert, voice, pain, unresponsive).
• Cardiovascular: BP, pulse rate and volume, and the shock index (heart rate ÷ systolic BP). The shock index is more useful than hypotension or tachycardia alone; levels >1.7 mean urgent intervention is needed. Use the obstetric shock index calculator.

Remark: CTG = cardiotocography; AVPU = alert, responds to voice, responds to pain, unresponsive.

Hypovolaemic shock

It is reversible with early diagnosis and early intervention:

• Put her in the left lateral position.
• Supplemental oxygen.
• Secure IV access.
• Aggressive replacement of the intravascular volume.
• Arrest the blood loss (see the PPH note).

Crystalloids vs colloids

Blood and blood products (packed cells, FFP, cryoprecipitate, cell salvage) increase oxygen delivery. End points of fluid therapy: urine output >0.5 mL/kg/h, MAP >65 mmHg, CVP >4 mmHg.

Remark: FFP = fresh frozen plasma; MAP = mean arterial pressure; CVP = central venous pressure.

Other types of shock

General management: resuscitation, early ventilation, maintain cardiac output and BP, and aggressive correction of coagulopathy with blood and blood products.

• Amniotic fluid embolism: rare, sudden and unpredictable, with mortality up to 60%. Suspect it in a sudden collapse with coagulopathy. The course may be immunogenic rather than embolic: fetal particulate matter triggers a severe anaphylactoid reaction and DIC. Risk factors include induction of labour, amniotomy, caesarean section and uterine rupture.
• Cardiogenic shock: rare, mortality up to 25%. Complications are left ventricular dysfunction, multi-organ failure and death. Manage with a multidisciplinary team, using diuretics, vasodilators, vasopressors, inotropes and thrombolytic therapy as indicated.
• Neurogenic shock: severe disturbance of the sympathetic nervous system causes peripheral vasodilatation, pooling of blood away from the heart and sudden hypotension. Causes include uterine inversion, manual removal of placenta and uterine rupture.

Remark: DIC = disseminated intravascular coagulation.

Take-home messages

• Perform CPR immediately if the pulse is absent or you are unsure.
• Left uterine displacement is essential to improve maternal circulation.
• Perform resuscitative hysterotomy within 4 minutes of collapse.
• Prevent shock with simulation training, guidelines and care bundles, good documentation and audit.

Sources

• Obstetric Life Saving Skills (OLSS) lectures: Maternal Collapse and Maternal Shock and Resuscitation. Hospital Sultan Haji Ahmad Shah (HOSHAS), Temerloh, 2026.
• Obstetrical and Gynaecological Society of Malaysia (OGSM). Handbook of Obstetric Emergencies (ICOE): figures on the physiological changes of pregnancy, assessment of a mother in shock, clinical features of blood loss and fluids for hypovolaemic shock, as reproduced in the lectures.