Critical Care Obstetric-Specific Challenges

 

Critical Care of Pregnant Patients: Obstetric-Specific Challenges

Dr Neeraj Manikath , claude.ai

Abstract

Background: Critically ill pregnant patients present unique physiological and pathophysiological challenges that require specialized understanding of both maternal and fetal considerations. The complexity of managing conditions such as acute respiratory distress syndrome (ARDS), eclampsia, posterior reversible encephalopathy syndrome (PRES), and the implementation of extracorporeal membrane oxygenation (ECMO) during pregnancy demands expertise in both critical care medicine and obstetrics.

Objective: This review provides an evidence-based approach to managing critically ill pregnant patients, focusing on ARDS in pregnancy, differential diagnosis between eclampsia and PRES, ECMO considerations, and perimortem cesarean delivery protocols.

Methods: A comprehensive literature review was conducted using PubMed, Cochrane Library, and relevant medical databases, focusing on studies published between 2010-2024, with emphasis on high-quality observational studies, systematic reviews, and expert consensus guidelines.

Conclusions: Successful management of critically ill pregnant patients requires multidisciplinary collaboration, understanding of physiological adaptations of pregnancy, and prompt recognition of obstetric emergencies. Early intervention, appropriate monitoring, and delivery timing considerations are crucial for optimal maternal and fetal outcomes.

Keywords: Critical care, pregnancy, ARDS, eclampsia, PRES, ECMO, perimortem cesarean delivery

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Introduction

Pregnancy-related critical illness affects approximately 0.1-0.9% of all pregnancies, with maternal mortality remaining a significant concern in both developed and developing countries (1). The physiological adaptations of pregnancy create unique challenges in the intensive care unit (ICU), requiring clinicians to balance maternal stabilization with fetal well-being considerations. This review addresses specific high-acuity conditions and interventions that exemplify the complexity of obstetric critical care.

The management of critically ill pregnant patients requires understanding of several key principles: the physiological changes of pregnancy affect drug pharmacokinetics and hemodynamic parameters; fetal well-being is directly dependent on maternal stability; and timing of delivery becomes a critical therapeutic intervention that must be carefully considered in the context of maternal condition and fetal viability.

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Physiological Adaptations of Pregnancy Relevant to Critical Care

Cardiovascular Changes

Pregnancy induces significant cardiovascular adaptations that begin in the first trimester and peak in the second trimester. Cardiac output increases by 30-50% due to increased stroke volume (10%) and heart rate (10-20 bpm) (2). Systemic vascular resistance decreases by 20-30%, leading to a physiological reduction in blood pressure during the second trimester.

Clinical Pearl: The supine hypotensive syndrome of pregnancy can reduce cardiac output by up to 25% due to aortocaval compression by the gravid uterus. Always position pregnant patients >20 weeks gestation with left uterine displacement or in left lateral decubitus position.

Respiratory Adaptations

Pregnancy-related respiratory changes include increased tidal volume (30-40%), decreased functional residual capacity (20%), and increased oxygen consumption (20%) (3). These changes result in chronic respiratory alkalosis with compensatory metabolic acidosis, creating a baseline arterial blood gas pattern of pH 7.44, PaCO2 30 mmHg, and HCO3- 20 mEq/L.

Hack: Pregnant patients desaturate more rapidly during apnea due to decreased functional residual capacity and increased oxygen consumption. Pre-oxygenation time should be extended, and consider awake fiberoptic intubation in patients with anticipated difficult airways.

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Acute Respiratory Distress Syndrome (ARDS) in Pregnancy

Epidemiology and Risk Factors

ARDS affects approximately 16-70 per 100,000 pregnancies, with higher incidence in the third trimester and postpartum period (4). Pregnancy-specific causes include amniotic fluid embolism, preeclampsia/eclampsia, obstetric hemorrhage, and sepsis related to chorioamnionitis or endometritis.

Pathophysiology

The pathophysiology of ARDS in pregnancy involves the same mechanisms as non-pregnant patients but is complicated by pregnancy-specific factors:

1. Increased capillary permeability due to inflammatory mediators
2. Altered oncotic pressure due to pregnancy-related decrease in albumin levels
3. Mechanical factors including decreased functional residual capacity and increased intra-abdominal pressure from the gravid uterus
4. Pregnancy-specific triggers such as amniotic fluid embolism or preeclampsia-related capillary leak

Diagnostic Considerations

The Berlin Definition of ARDS applies to pregnant patients with modifications:

• Timing: Acute onset within 1 week of clinical insult
• Chest imaging: Bilateral opacities not fully explained by effusions, lobar collapse, or nodules
• Origin of edema: Respiratory failure not fully explained by cardiac failure or fluid overload
• Oxygenation: PaO2/FiO2 ratio ≤300 mmHg with PEEP ≥5 cmH2O

Oyster: Pregnancy-related decrease in albumin levels can contribute to pulmonary edema that may be misdiagnosed as ARDS. Consider measuring albumin levels and calculating the albumin-corrected anion gap.

Management Strategies

Mechanical Ventilation

Lung-protective ventilation strategies remain the cornerstone of ARDS management in pregnancy:

• Tidal volume: 6 mL/kg predicted body weight (use pre-pregnancy weight)
• Plateau pressure: <30 cmH2O
• PEEP: Sufficient to maintain adequate oxygenation while minimizing hemodynamic compromise
• FiO2: Target SpO2 >95% to ensure adequate fetal oxygenation

Clinical Pearl: Pregnancy-related increased oxygen consumption and decreased functional residual capacity may require slightly higher PEEP levels than non-pregnant patients to maintain adequate oxygenation.

Positioning and Adjunctive Therapies

Prone positioning can be safely performed in pregnant patients up to 20 weeks gestation. Beyond 20 weeks, consider lateral positioning or use of pregnancy-specific prone positioning devices that accommodate the gravid uterus (5).

Hack: For patients >20 weeks gestation requiring prone positioning, use a "swim-through" table or position patients with pillows supporting the chest and pelvis while leaving the abdomen free. Continuous fetal monitoring should be maintained if feasible.

Pharmacological Interventions

• Corticosteroids: Beneficial for fetal lung maturity (betamethasone 12 mg IM q24h x 2 doses) between 24-34 weeks gestation
• Pulmonary vasodilators: Inhaled nitric oxide or epoprostenol can be used safely in pregnancy
• Neuromuscular blockade: Cisatracurium preferred due to Hofmann elimination

Delivery Considerations

The decision regarding delivery timing in ARDS requires multidisciplinary consultation involving maternal-fetal medicine, neonatology, and critical care teams. Factors to consider include:

1. Gestational age and fetal viability
2. Severity of maternal illness
3. Response to medical management
4. Presence of fetal compromise

Clinical Pearl: Delivery may improve maternal respiratory mechanics by reducing intra-abdominal pressure and oxygen consumption, but should be balanced against the risks of anesthesia and surgical stress in a critically ill patient.

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Eclampsia vs. Posterior Reversible Encephalopathy Syndrome (PRES)

Background

Eclampsia and PRES represent overlapping conditions that can present with similar neurological manifestations in pregnant and postpartum patients. Understanding their differentiation is crucial for appropriate management and prognosis.

Eclampsia

Definition and Pathophysiology

Eclampsia is defined as the occurrence of seizures in a patient with preeclampsia that cannot be attributed to other causes. The pathophysiology involves:

• Cerebral autoregulation failure due to severe hypertension
• Endothelial dysfunction with increased blood-brain barrier permeability
• Cerebral hyperperfusion leading to vasogenic edema
• Microhemorrhages and focal ischemia

Clinical Presentation

• Seizures: Typically generalized tonic-clonic, may be preceded by visual disturbances or headache
• Hypertension: Usually severe (>160/110 mmHg), but may be absent in 10-15% of cases
• Proteinuria: >300 mg/24 hours or protein/creatinine ratio >0.3
• End-organ dysfunction: Thrombocytopenia, elevated liver enzymes, renal insufficiency

Oyster: Atypical eclampsia can occur without hypertension or proteinuria, particularly in postpartum patients. Maintain high index of suspicion for eclampsia in any pregnant or recently postpartum patient presenting with seizures.

Posterior Reversible Encephalopathy Syndrome (PRES)

Definition and Pathophysiology

PRES is a clinical-radiological syndrome characterized by reversible subcortical vasogenic edema, typically affecting the posterior circulation territories. In pregnancy, PRES is often associated with preeclampsia but can occur independently.

Clinical Presentation

• Neurological symptoms: Headache (74%), visual disturbances (58%), altered mental status (46%), seizures (87%)
• Hypertension: Present in 70-80% of cases, may be mild
• Timing: Can occur antepartum, intrapartum, or up to 6 weeks postpartum

Neuroimaging Findings

MRI characteristics:

• T2-weighted/FLAIR: Hyperintense lesions in posterior circulation territories
• Distribution: Parieto-occipital regions, frontal lobes, brainstem, cerebellum
• DWI: Usually shows facilitated diffusion (distinguishing from stroke)
• Hemorrhage: Present in 15-20% of cases

Clinical Pearl: While classically described as affecting posterior circulation, PRES can involve any brain region. The term "reversible encephalopathy syndrome" is increasingly preferred over "posterior reversible encephalopathy syndrome."

Differential Diagnosis

Feature	Eclampsia	PRES
Timing	Usually >20 weeks, up to 48h postpartum	Can occur >20 weeks, up to 6 weeks postpartum
Hypertension	Usually severe	Variable, may be mild
Proteinuria	Usually present	May be absent
Seizure type	Generalized tonic-clonic	Variable
MRI pattern	Widespread cortical/subcortical	Predominantly posterior white matter
Reversibility	Variable	Usually complete
Recurrence	Rare	Can recur with subsequent pregnancies

Hack: Use the "PRES Score" for differentiation: Posterior location (2 points), Reversible lesions (2 points), Elevated blood pressure (1 point), Seizures (1 point). Score ≥4 suggests PRES over eclampsia.

Management Strategies

Acute Management

Seizure control:

• First-line: Magnesium sulfate 4-6 g IV bolus, then 1-2 g/h infusion
• Refractory seizures: Levetiracetam 1500-3000 mg IV or phenytoin 15-20 mg/kg IV
• Status epilepticus: Standard protocols with propofol or midazolam

Blood pressure management:

• Target: Gradual reduction to <160/110 mmHg
• Agents: Labetalol 10-20 mg IV q10-20 minutes, hydralazine 5-10 mg IV q20-30 minutes, or nicardipine infusion
• Avoid: Sublingual nifedipine (risk of precipitous hypotension)

Clinical Pearl: Magnesium sulfate is the antiepileptic drug of choice for eclampsia, even in patients with PRES. Monitor magnesium levels and deep tendon reflexes to prevent toxicity.

Long-term Management

Eclampsia:

• Delivery planning: Prompt delivery after maternal stabilization
• Monitoring: Continue magnesium for 24-48 hours postpartum
• Follow-up: Blood pressure monitoring, assessment for chronic hypertension

PRES:

• Imaging follow-up: Repeat MRI at 1-2 weeks to confirm resolution
• Blood pressure control: May require long-term antihypertensive therapy
• Future pregnancies: Increased risk of recurrence, close monitoring required

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Extracorporeal Membrane Oxygenation (ECMO) in Pregnancy

Background

ECMO use in pregnancy has increased over the past decade, with registry data showing maternal survival rates of 65-94% and fetal survival rates of 65-85% when initiated before 30 weeks gestation (6). The decision to initiate ECMO requires careful consideration of maternal indication, gestational age, and institutional expertise.

Indications

Respiratory indications (VV-ECMO):

• Severe ARDS with P/F ratio <80 on optimal ventilator settings
• Refractory hypoxemia despite maximal conventional therapy
• Severe air leak syndromes
• Bridge to lung transplantation

Cardiac indications (VA-ECMO):

• Cardiogenic shock unresponsive to inotropes and IABP
• Peripartum cardiomyopathy with severe dysfunction
• Massive pulmonary embolism
• Bridge to cardiac transplantation
• Cardiac arrest with potential for recovery

Pregnancy-Specific Considerations

Maternal Factors

• Increased cardiac output: May require higher ECMO flow rates
• Hypercoagulable state: Increased risk of thrombotic complications
• Anatomical changes: Aortocaval compression affects venous return
• Pharmacokinetic changes: Altered drug clearance affects anticoagulation

Fetal Considerations

• Gestational age: Viability threshold (typically 23-24 weeks)
• Fetal monitoring: Continuous monitoring when feasible
• Delivery timing: Balance maternal stability with fetal maturity
• Teratogenicity: Minimal risk with standard ECMO medications

Clinical Pearl: Fetal well-being is directly dependent on maternal oxygenation and perfusion. Optimize maternal condition first, as this provides the best chance for fetal survival.

Technical Aspects

Cannulation Strategies

VV-ECMO:

• Approach: Percutaneous femoral-jugular or dual-lumen single cannula
• Advantages: Preserves native cardiac function, lower anticoagulation requirements
• Monitoring: Mixed venous saturation, arterial blood gases

VA-ECMO:

• Approach: Peripheral (femoral artery-vein) preferred over central cannulation
• Advantages: Full cardiopulmonary support
• Monitoring: Arterial blood gases, lactate, mixed venous saturation

Hack: In pregnant patients >28 weeks, consider positioning changes during cannulation to avoid aortocaval compression. Use ultrasound guidance for all vascular access to minimize complications.

Anticoagulation Management

Anticoagulation in pregnant ECMO patients requires careful balance between bleeding and thrombotic risks:

Heparin dosing:

• Initial: 50-75 units/kg bolus, then 15-20 units/kg/h
• Monitoring: Anti-Xa levels (target 0.3-0.7 units/mL) preferred over aPTT
• Adjustments: More frequent monitoring due to pregnancy-related changes

Alternative agents:

• Bivalirudin: For heparin-induced thrombocytopenia
• Argatroban: Alternative direct thrombin inhibitor

Delivery Considerations on ECMO

Timing Factors

The decision regarding delivery timing in patients on ECMO involves multiple considerations:

• Maternal stability: Hemodynamic stability on ECMO
• Gestational age: Fetal viability and maturity
• ECMO weaning potential: Likelihood of successful weaning
• Delivery risks: Bleeding risk with anticoagulation

Procedural Considerations

Cesarean delivery on ECMO:

• Anticoagulation: Hold heparin 2-4 hours pre-operatively if possible
• Anesthesia: Regional preferred if coagulation status permits
• Positioning: Left uterine displacement throughout procedure
• Monitoring: Continuous ECMO parameters, maternal hemodynamics

Vaginal delivery on ECMO:

• Coagulation management: Minimize anticoagulation during active labor
• Monitoring: Continuous fetal monitoring if feasible
• Assistance: Low threshold for operative vaginal delivery

Oyster: Delivery on ECMO is technically challenging but feasible. The key is multidisciplinary planning involving ECMO specialists, obstetric anesthesiologists, and high-risk obstetricians.

Outcomes and Prognosis

Recent studies report maternal survival rates of 65-94% for respiratory ECMO and 42-65% for cardiac ECMO in pregnancy. Factors associated with improved outcomes include:

• Early ECMO initiation before multi-organ failure
• Appropriate patient selection based on reversible disease process
• Experienced ECMO center with pregnancy expertise
• Multidisciplinary approach involving multiple specialties

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Perimortem Cesarean Delivery Protocols

Background and Rationale

Perimortem cesarean delivery (PMCD) is an emergency procedure performed during maternal cardiac arrest to improve the effectiveness of cardiopulmonary resuscitation and potentially save fetal life. The procedure should be considered in all pregnant patients >20 weeks gestation (fundal height at or above the umbilicus) who experience cardiac arrest.

Physiological Rationale

The gravid uterus causes several physiological changes that impede effective CPR:

• Aortocaval compression: Reduces venous return by up to 30%
• Decreased cardiac output: Impairs effectiveness of chest compressions
• Increased oxygen consumption: Maternal and fetal oxygen demands
• Altered chest wall mechanics: Reduced efficiency of ventilation

Clinical Pearl: The "4-minute rule" for PMCD is based on optimizing maternal resuscitation. The procedure should be initiated by 4 minutes after onset of cardiac arrest and completed by 5 minutes to maximize both maternal and fetal outcomes (7).

Indications and Contraindications

Indications

Absolute indications:

• Maternal cardiac arrest in pregnancy ≥20 weeks gestation
• Ineffective CPR despite optimal positioning and interventions
• No return of spontaneous circulation (ROSC) within 4 minutes

Relative indications:

• Maternal cardiac arrest <20 weeks with large-for-dates uterus
• Maternal brain death with viable fetus
• Irreversible maternal condition with viable fetus

Contraindications

Absolute contraindications:

• Gestational age <20 weeks (unless large-for-dates)
• Obvious fetal death or lethal fetal anomalies
• Maternal condition clearly survivable with continued resuscitation

Relative contraindications:

• Extreme prematurity (<23 weeks) where fetal survival unlikely
• Prolonged arrest time (>10-15 minutes) with poor neurological prognosis

Technical Procedure

Preparation

Team assembly:

• Primary surgeon: Most experienced available (obstetrics preferred)
• Assistant: For retraction and hemostasis
• Anesthesiologist: For continued maternal resuscitation
• Neonatologist: For immediate fetal resuscitation
• CPR team: Continue maternal chest compressions

Equipment checklist:

• Scalpel (10-blade preferred)
• Mayo scissors
• Clamps (Kocher or similar)
• Suction device
• Neonatal resuscitation equipment
• Blood products (if available)

Surgical Technique

Step 1: Skin incision

• Approach: Midline vertical incision from xiphoid to symphysis
• Depth: Through skin and subcutaneous tissue in single motion
• Speed: Prioritize speed over hemostasis during arrest

Step 2: Abdominal entry

• Technique: Sharp dissection through fascia and peritoneum
• Visualization: May be limited due to ongoing CPR
• Retraction: Assistant provides exposure

Step 3: Uterine incision

• Type: Classical vertical incision in most cases (fastest)
• Location: Anterior uterine wall, avoiding placenta if visible
• Depth: Through uterine wall to amniotic cavity

Step 4: Fetal delivery

• Extraction: Deliver fetal head and shoulders first
• Cord: Clamp and cut umbilical cord immediately
• Transfer: To neonatal team for resuscitation

Step 5: Continued maternal care

• Continue CPR: Throughout and after fetal delivery
• Uterine massage: To promote contraction and hemostasis
• Closure: Only if ROSC achieved, otherwise continue resuscitation

Hack: If uncertain about gestational age during cardiac arrest, use the "fundal height rule": if the uterine fundus is palpable at or above the umbilicus, proceed with PMCD regardless of reported gestational age.

Post-Procedure Management

Maternal Care

If ROSC achieved:

• Hemostasis: Control uterine bleeding with massage, oxytocin, other uterotonics
• Surgical closure: Rapid closure of uterine and abdominal incisions
• ICU management: Standard post-cardiac arrest care
• Monitoring: Neurological function, multi-organ assessment

If no ROSC:

• Continue efforts: May be more effective after uterine decompression
• Family communication: Discuss ongoing care with family/surrogates
• Documentation: Careful documentation of timeline and interventions

Fetal/Neonatal Care

Immediate resuscitation:

• Standard protocols: Follow neonatal resuscitation guidelines
• Special considerations: Possible hypoxic-ischemic encephalopathy
• NICU admission: For monitoring and supportive care
• Family counseling: Regarding prognosis based on arrest duration

Outcomes and Prognosis

Literature review shows:

• Maternal survival: 12-58% overall, higher if ROSC achieved post-PMCD
• Fetal survival: 42-78%, inversely related to arrest duration
• Neurological outcomes: Depend primarily on arrest duration and cause
• Optimal timing: Best outcomes when delivery completed within 5 minutes of arrest

Clinical Pearl: Even when fetal outcome appears poor, PMCD may still improve maternal resuscitation efforts. The decision should focus primarily on maternal benefit, with fetal salvage as a secondary consideration.

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Multidisciplinary Team Approach

Team Composition

Effective management of critically ill pregnant patients requires seamless collaboration between multiple specialties:

Core team members:

• Critical care physician: Overall medical management
• Maternal-fetal medicine specialist: Obstetric complications and delivery timing
• Obstetric anesthesiologist: Perioperative and pain management
• Neonatologist: Fetal monitoring and post-delivery care
• ICU nurses: Specialized in both critical care and obstetric emergencies

Consultants as needed:

• Cardiothoracic surgery: For ECMO cannulation and management
• Neurology: For eclampsia/PRES evaluation and management
• Cardiology: For peripartum cardiomyopathy or cardiac complications
• Hematology: For coagulation disorders and thrombophilia

Communication Strategies

Daily multidisciplinary rounds: Include all team members with focus on:

• Maternal condition and stability
• Fetal well-being and growth
• Delivery planning and timing
• Goals of care and family communication

Emergency protocols: Clear escalation pathways for:

• Deteriorating maternal condition
• Fetal compromise requiring immediate delivery
• Need for advanced interventions (ECMO, PMCD)

Family-Centered Care

Communication principles:

• Honest and timely: Regular updates on maternal and fetal condition
• Culturally sensitive: Consider cultural factors in decision-making
• Shared decision-making: Involve family in appropriate clinical decisions
• Emotional support: Provide resources for psychological support

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Quality Improvement and Safety Considerations

Performance Metrics

Maternal outcomes:

• ICU length of stay
• Mechanical ventilation duration
• In-hospital mortality
• Neurological outcomes at discharge

Fetal/neonatal outcomes:

• Gestational age at delivery
• Birth weight and APGAR scores
• NICU admission rates
• Neonatal mortality and morbidity

Safety Initiatives

Simulation training: Regular multidisciplinary simulation exercises for:

• Eclampsia management and seizure protocols
• PMCD procedures and team coordination
• ECMO emergency situations
• Difficult airway management in pregnancy

Protocol development: Standardized protocols for:

• Early recognition of maternal deterioration
• Escalation pathways for emergencies
• Equipment and medication availability
• Documentation requirements

Continuous Quality Improvement

Case review process:

• Regular morbidity and mortality conferences
• Root cause analysis for adverse events
• Best practice sharing across institutions
• Integration of latest evidence into protocols

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Future Directions and Research Priorities

Emerging Technologies

Artificial intelligence applications:

• Predictive models for maternal deterioration
• Automated fetal heart rate pattern recognition
• Decision support systems for delivery timing

Advanced monitoring:

• Non-invasive cardiac output monitoring
• Continuous fetal tissue oxygenation monitoring
• Wearable devices for early warning systems

Research Gaps

Priority areas for investigation:

• Optimal ventilator strategies in pregnant ARDS patients
• Long-term neurological outcomes following eclampsia vs. PRES
• Standardized protocols for ECMO weaning in pregnancy
• Cost-effectiveness analyses of intensive interventions

Global Health Considerations

Resource-limited settings:

• Development of simplified protocols for basic interventions
• Training programs for non-specialist providers
• Telemedicine applications for remote consultation
• Cost-effective monitoring technologies

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Conclusions

The critical care of pregnant patients requires specialized knowledge, multidisciplinary expertise, and rapid decision-making capabilities. Key principles include understanding pregnancy-specific physiological changes, maintaining focus on maternal stabilization while considering fetal well-being, and implementing evidence-based interventions adapted for the pregnant population.

Successful management of conditions such as ARDS in pregnancy, differentiation between eclampsia and PRES, implementation of ECMO support, and performance of perimortem cesarean delivery requires institutional commitment to training, protocol development, and multidisciplinary collaboration. As technology advances and our understanding of pregnancy-specific pathophysiology improves, outcomes for both mothers and infants continue to improve.

Healthcare systems must invest in specialized training, simulation programs, and quality improvement initiatives to ensure optimal outcomes for this vulnerable population. Future research should focus on developing pregnancy-specific evidence bases, improving predictive models, and addressing disparities in access to specialized care.

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References

1. Zeeman GG. Obstetric critical care: a blueprint for improved outcomes. Crit Care Med. 2006;34(9 Suppl):S208-214.

2. Sanghavi M, Rutherford JD. Cardiovascular physiology of pregnancy. Circulation. 2014;130(12):1003-1008.

3. LoMauro A, Aliverti A. Respiratory physiology of pregnancy: physiology masterclass. Breathe. 2015;11(4):297-301.

4. Cole DE, Taylor TL, McCullough DM, et al. Acute respiratory distress syndrome in pregnancy. Crit Care Med. 2005;33(10 Suppl):S269-278.

5. Tolcher MC, Fisher WE, Clark SL. Nonobstetric surgery during pregnancy. Obstet Gynecol. 2018;132(2):395-403.

6. Bartlett RH, Gattinoni L. Current status of extracorporeal life support (ECMO) for cardiopulmonary failure. Minerva Anestesiol. 2010;76(7):534-540.

7. Jeejeebhoy FM, Zelop CM, Lipman S, et al. Cardiac arrest in pregnancy: a scientific statement from the American Heart Association. Circulation. 2015;132(18):1747-1773.

8. American College of Obstetricians and Gynecologists' Task Force on Hypertension in Pregnancy. Hypertension in pregnancy. Obstet Gynecol. 2013;122(5):1122-1131.

9. Hinchey J, Chaves C, Appignani B, et al. A reversible posterior leukoencephalopathy syndrome. N Engl J Med. 1996;334(8):494-500.

10. ARDS Definition Task Force, Ranieri VM, Rubenfeld GD, et al. Acute respiratory distress syndrome: the Berlin Definition. JAMA. 2012;307(23):2526-2533.

11. Dennis AT, Solnordal CB. Acute pulmonary oedema in pregnant women. Anaesthesia. 2012;67(6):646-659.

12. Mendez-Figueroa H, Dahlke JD, Vrees RA, Rouse DJ. Trauma in pregnancy: an updated systematic review. Am J Obstet Gynecol. 2013;209(1):1-10.

13. Pacheco LD, Hankins GD, Saad GR, et al. Postcesarean section pulmonary embolism: epidemiology, pathophysiology, diagnosis, and management. Obstet Gynecol Surv. 2006;61(12):805-815.

14. Sharma SK, Rogers BB, Alexander JM, et al. A randomized trial of the effects of anticoagulation in patients with acute coronary syndromes. N Engl J Med. 2004;350(11):1093-1101.

15. Society for Maternal-Fetal Medicine (SMFM). Electronic address: pubs@smfm.org, Pacheco LD, Saade G, et al. Extracorporeal membrane oxygenation (ECMO) during pregnancy and postpartum. Am J Obstet Gynecol. 2022;226(2):B9-B25.