Amniotic fluid embolism: incidence, risk factors, and impact on perinatal outcome

Extracorporeal Membrane Oxygenation in Amniotic Fluid Embolism: A Systematic Review of Case Reports

Amniotic fluid embolism (AFE) is an obstetric complication that can result in acute circulatory failure during and after labor. The effectiveness of extracorporeal membrane oxygenation (ECMO) in AFE patients has not been established, especially in the context of coagulopathy. This review aims to evaluate the efficacy of ECMO support in AFE patients. We conducted a systematic review of case reports following the Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Quality assessment was performed using a standardized tool. Out of 141 studies screened, 33 studies included 79 AFE patients. The median age was 34 years, and the median gestational age was 37.5 weeks. The majority of AFE cases occurred during cesarean section delivery (55.2%), followed by labor before fetal delivery (26.7%). Extracorporeal membrane oxygenation configurations included venoarterial ECMO (81.3%) and extracorporeal cardiopulmonary resuscitation (CPR, 10.7%). The maternal survival rate was 72%, with 21.2% experiencing minor neurological sequelae and 5.8% having major neurological sequelae. Rescue ECMO to support circulation has demonstrated both safety and efficacy in managing AFE. We suggest early activation of local or mobile ECMO as soon as an AFE diagnosis is established. Further studies are needed to assess the benefits and implications of early ECMO support in AFE patients.

Amniotic Fluid Embolism: a comparison of two classification systems in a retrospective 8-year analysis from two tertiary hospitals

OBJECTIVE

Amniotic fluid embolism (AFE) is a rare life-threatening complication in obstetrics, but the diagnosis lacks a consensual definition. The objective of this study was to compare two different AFE classification systems by analysing the AFE cases from two university hospitals.

MATERIAL AND METHODS

In this retrospective study, all patients with a strong suspicion of AFE between 2014 and 2021 at two university hospitals, LMU Women's University Hospital Munich, and Women's University Hospital Basel, were included. Patient records were checked for the ICD-10 code O88.1 (AFE). Diagnoses were confirmed through clinical findings and/or autopsy. The presence of the diagnostic criteria of the Society of Maternal Fetal Medicine (SMFM) and the AFE Foundation (AFEF) and of a new framework by Ponzio-Klijanienko et al. from Paris, France, were checked and compared using Chi-square-test.

RESULTS

Within our study period, 38,934 women delivered in the two hospitals. Six patients had a strong suspicion of AFE (0.015%). Only three of six patients (50%) presented with all the four diagnostic criteria of the SMFM/AFEF framework. All six patients met the criteria of the modified "Paris AFE framework".

CONCLUSION

Using the "Paris AFE framework" based exclusively on clinical criteria can help clinicians to diagnose AFE, anticipate the life-threatening condition of the patient and prepare immediately for best clinical care.

Fatal amniotic fluid embolism: incidence, risk factors and influence on perinatal outcome

PURPOSE

This study aimed to estimate the incidence of fatal amniotic fluid embolism, describe its risk factors, and analyze perinatal outcomes.

METHODS

Maternity cases and newborn records of amniotic fluid embolism were collected from the Zhejiang Maternal Surveillance System from October 2006 to October 2019. This study strictly limited the diagnostic criteria for AFE and excluded suspicious cases in order to minimize false-positive AFE cases. The risk factors of fatal amniotic fluid embolism and the relationship between perinatal prognosis and AFE were investigated using logistic regression analysis, estimating the adjusted odds ratios (aORs) and 95% confidence intervals (CIs).

RESULTS

149 cases of amniotic fluid embolism were registered, of which 80 cases were fatal. The estimated fatal AFE incidence was 0.99 per 100,000. The occurrence of fatal AFE was significantly correlated with spontaneous vaginal delivery (aOR 12.3, 95% CI 3.3-39.2) and cardiac arrest (aOR 64.8, 95% CI 14.6-287.8). The average diagnosis time of fatal AFE is 85.51 min, and the peak period of female death is 1-12 h after the onset of the disease, accounting for 60% (48/80) of cases. Fatal amniotic embolism is a cause of intrauterine fetal death and fetal death during delivery (aOR 11.957, 95% CI 1.457-96.919; aOR 13.152, 95% CI 1.636-105.723). Of the 149 confirmed AFE cases, 11 cases of stillbirth occurred, 12 cases were stillborn, and 7 cases of neonatal death were reported. The perinatal mortality rate was 202 per 1000.

CONCLUSIONS

Early detection, diagnosis, and treatment of amniotic fluid embolism are essential to avoiding fatal AFE. Clinicians should fully evaluate the pros and cons of choosing the delivery method for pregnant women. When cardiac arrest occurs in women with amniotic fluid embolism, obstetricians should be particularly careful and provide timely and effective treatment to minimize the fatality rate. The outcome of AFE is not only related to maternal survival but also plays a decisive role in the prognosis of the infant over the perinatal period.

Acute respiratory distress and amniotic fluid embolism in pregnancy

Respiratory failure in pregnant and postpartum women is uncommon, but it is one of the leading causes of maternal admission into the intensive care unit and is associated with high mortality. The underlying causes include sequelae of underlying medical conditions, such as congenital heart diseases, but it is more often related to acute respiratory distress syndrome from obstetric complications like pre-eclampsia, effect of treatment like tocolysis, coincidental to pregnancy like transfusion-related acute lung injury, and accidental like amniotic fluid embolism. The pathophysiological mechanisms involved in many of these conditions remain to be clearly established, but maternal inflammatory response and activation of the immune and complement systems appear to play leading roles. Prompt recognition of maternal respiratory distress and related manifestations and aggressive and adequate supportive treatment, especially cardiopulmonary resuscitation, ventilation, maintenance of circulation, and timely termination of the pregnancy, play key roles in achieving survival of both mother and foetus.

Pulmonary Embolism and Amniotic Fluid Embolism

Venous thromboembolism (VTE) as well as other embolic events including amniotic fluid embolism (AFE) remain a leading cause of maternal death in the United States and worldwide. The pregnant patient is at a higher risk of developing VTE including pulmonary embolism. In contrast, AFE is a rare, but catastrophic event that remains incompletely understood. Here the authors review the cause of VTE in pregnancy and look at contemporary and evidence-based practices for the evaluation, diagnosis, and management in pregnancy. Then the cause and diagnostic difficulty of AFE as well as what is known regarding the pathogenesis are reviewed.

A case report of early application of veno-arterial extracorporeal membrane oxygenation in amniotic fluid embolism

RATIONALE

Amniotic fluid embolism (AFE) is a rare obstetrical complication and is a leading cause of maternal death in developed countries. Despite the development of supportive therapeutic measures, the mortality rate remains high.

PATIENT CONCERNS

A 38-year-old nulliparous pregnant woman, who underwent in vitro fertilization-embryo transfer, was admitted for labor at 37 weeks' gestation. Approximately 30 minutes after delivery of the placenta, the puerpera developed postpartum hemorrhage with uterine atony. Soon after, the patient experienced hypotension, repeated cardiac arrest, refectory hypoxia, and disseminated intravascular coagulopathy.

DIAGNOSIS

AFE is diagnosed clinically. The pregnant woman in this case fulfilled the diagnostic criteria for AFE: acute hypotension, cardiac arrest, acute hypoxia, and coagulation disorders within approximately 30 minutes after delivery of the placenta.

INTERVENTIONS

The patient was intubated, connected to a ventilator, and was administered a high dose of vasoactive drugs to maintain blood pressure and underwent an emergency hysterectomy. Considering the risk for recurrent cardiac arrest and severe refractory hypoxia, venoarterial extracorporeal membrane oxygenation was initiated and discontinued as soon as cardiac function was restored based on serial bedside ultrasound assessment.

OUTCOMES

The patient stabilized on day 7 in the intensive care unit and was transferred to the obstetrics ward and, 1 week later, was discharged with no complications. Two months later, follow-up revealed that the patient was in good condition.

LESSON

Serial bedside ultrasound was crucial for assessing cardiac function and optimal weaning. Timely application of venoarterial extracorporeal membrane oxygenation and weaning was significant to avoid the occurrence of complications and improve long-term outcomes.

Anesthesia-related adverse events in obstetric patients: a population-based study in Canada

BACKGROUND

Anesthesia-related complications in obstetric patients could be catastrophic and impact the lives of both the parturient and the neonate. The objective of this study was to determine the frequency, temporal trend, and risk factors of anesthesia-related adverse events during hospitalization for delivery in Canada.

METHODS

This retrospective population-based study utilized the hospitalization database of the Canadian Institute for Health Information for all parturients (gestation ≥ 20 weeks) in Canada (except Quebec) hospitalized for childbirth from April 2004 to March 2017. Complications were identified by the enhanced Canadian version of the tenth revision of the International Statistical Classification of Diseases and Related Health Problems codes. Data were summarized with descriptive statistics. Associations between hospitalizations with an anesthesia-related adverse event and patient characteristics, delivery method, and modality of anesthesia were assessed using multivariate logistic regression.

RESULTS

Among 2,601,034 hospitalizations (3,194,875 interventions), 8,361 anesthesia-related adverse events occurred over a 13-year period (262 per 100,000 interventions; 95% confidence interval [CI], 256 to 267), with a significant decline over time (P < 0.001). These were two-fold and seven-fold higher per 100,000 interventions with general (488; 95% CI, 438 to 542) and general plus neuraxial (1,476; 95% CI, 1,284 to 1,689) anesthesia compared with neuraxial anesthesia alone (225; 95% CI, 219 to 230). Serious adverse events constituted 9% of all adverse events. The most common adverse event was spinal and epidural anesthesia-induced headache (6,908/8,361; 83%); the overall rate of failed or difficult intubations was low (201/8,361; 2%). Anesthesia-related events were more likely in those who had a Cesarean delivery compared with vaginal delivery (odds ratio [OR], 1.12; 95% CI, 1.06 to 1.18) and general anesthesia compared with neuraxial anesthesia (OR, 1.71; 95% CI, 1.53 to 1.93). Noteworthy associations were found between any anesthesia-related adverse events and cardiomyopathy (OR, 8.34; 95% CI, 2.59 to 26.83), eclampsia (OR, 3.11; 95% CI, 1.95 to 4.97), and obstructive sleep apnea (OR, 1.91; 95% CI, 1.66 to 2.19).

CONCLUSION

The incidence of anesthesia-related adverse events in obstetric patients in Canada is low and declining. High vigilance is required in parturients undergoing Cesarean delivery, receiving general anesthesia, and those with pre-existing medical conditions.

The role of echocardiography in amniotic fluid embolism: a case series and review of the literature

PURPOSE

Amniotic fluid embolism (AFE) is a rare, but often fatal condition characterized by sudden hemodynamic instability and coagulopathy occurring during labour or in the early postpartum period. As the mechanisms leading to shock and the cardiovascular effects of AFE are incompletely understood, the purpose of this case series is to describe how AFE presents on echocardiography and review limited reports in the literature.

CLINICAL FEATURES

We describe three cases of AFE at the Jewish General Hospital, a tertiary care centre in Montreal, Canada. All cases met the Clark diagnostic criteria, which comprise 1) sudden cardiorespiratory arrest or both hypotension and respiratory compromise, 2) disseminated intravascular coagulation, 3) clinical onset during labour or within 30 min of delivery of the placenta, and 4) absence of fever. Two patients had a cardiac arrest and the third developed significant hypotension and hypoxia. In all patients, point-of-care echocardiography at the time of shock revealed signs of right ventricular failure including a D-shaped septum, acute pulmonary hypertension, and right ventricular systolic dysfunction.

CONCLUSION

This case series and literature review of AFE emphasizes the importance of echocardiography in elucidating the etiology of maternal shock. The presence of right ventricular failure may be considered an important criterion to diagnose AFE.

Amniotic fluid embolism - implementation of international diagnosis criteria and subsequent pregnancy recurrence risk

OBJECTIVES

An international diagnostic criterion for amniotic fluid embolism (AFE) diagnosis has recently been published. Data regarding subsequent pregnancies is scarce. We sought to implement recent diagnostic criteria and detail subsequent pregnancies in survivors.

METHODS

A case series of all suspected AFE cases at a tertiary medical center between 2003 and 2018 is presented. Cases meeting the diagnostic criteria for AFE were included. Clinical presentation, treatment, and outcomes described. Pregnancy outcomes in subsequent pregnancies in AFE survivors detailed.

RESULTS

Between 2003 and 2018 14 women were clinically suspected with AFE and 12 of them (85.71%) met the diagnostic criteria for AFE. Three cases occurred during midtrimester dilation and evacuation procedures, and the remaining occurred in the antepartum period. Of the antepartum cases, mode of delivery was cesarean delivery or vacuum extraction for expedited delivery due to presentation of AFE in 8/9 cases (88.88%). Clinical presentation included cardiovascular collapse, respiratory distress and disseminated intravascular coagulopathy (DIC). Heart failure of varying severity was diagnosed in 75% (9/12) cases. Composite maternal morbidity was 5/12 (41.66%), without cases of maternal mortality. 11 subsequent pregnancies occurred in four AFE survivors. Pregnant women were followed by a high-risk pregnancy specialist and multidisciplinary team if pregnancy continued beyond the early second trimester. Six pregnancies resulted in a term delivery. No recurrences of AFE were documented.

CONCLUSIONS

Use of a diagnostic criterion for diagnosis of AFE results in a more precise diagnosis of AFE. Nevertheless, the accuracy of clinical diagnosis is still high. Subsequent pregnancies were not associated with AFE recurrence.

Consumptive Coagulopathy Involving Amniotic Fluid Embolism: The Importance of Earlier Assessments for Interventions in Critical Care

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Objectives:

Amniotic fluid embolism is a rare disease that induces fatal coagulopathy; however, due to its rarity, it has not yet been examined in detail. The strict diagnostic criteria by Clark for amniotic fluid embolism include severe coagulopathy complicated by cardiopulmonary insufficiency, whereas the Japanese criteria also include postpartum hemorrhage or Disseminated Intravascular Coagulation in clinical practice. Amniotic fluid embolism cases with preceding consumptive coagulopathy may exist and are potential clinical targets for earlier assessments and interventions among amniotic fluid embolism cases fulfilling the Japanese, but not Clark criteria. The present study was performed to compare coagulopathy in the earlier stage between the amniotic fluid embolism patients diagnosed by Clark criteria (Clark group, n = 6), those by the Japanese criteria (Non-Clark group, n = 10), and peripartum controls and identify optimal clinical markers for earlier assessments of amniotic fluid embolism-related consumptive coagulopathy.

Design:

Retrospective case-control study.

Setting:

A single university-based center. Our amniotic fluid embolism registry program has accumulated clinical information and blood samples since 2003.

Patients:

Amniotic fluid embolism patients in the Clark and Non-Clark groups between 2009 and 2017 and peripartum controls.

Interventions:

None.

Measurements and Main Results:

Clinical information was collected on hemoglobin levels, platelet counts, and coagulation- and fibrinolysis-related variables. Fibrinolytic parameters were also measured and compared among the three groups before blood transfusion. Fibrinogen levels in all patients in the Clark group and most in the Non-Clark group decreased earlier than hemoglobin levels, which was consistent with the high hemoglobin/fibrinogen ratio and, thus, is a promising clinical marker for the earlier assessment of amniotic fluid embolism-related consumptive coagulopathy.

Conclusions:

Earlier evaluations of consumptive coagulopathy and hyperfibrinolysis using the hemoglobin/fibrinogen ratio following preemptive treatment may reduce the occurrence or prevent the aggravation of severe coagulopathy in amniotic fluid embolism patients.

Fibrinogen may aid in the early differentiation between amniotic fluid embolism and postpartum haemorrhage: a retrospective chart review

This study aimed to determine whether blood loss and fibrinogen can differentiate amniotic fluid embolism (AFE) from postpartum haemorrhage (PPH). This retrospective case–control study included nine patients with clinical AFE (“AFE group”) and 78 patients with PPH managed at our tertiary care perinatal centre between January 2014 and March 2016. Patients meeting the Japanese diagnostic criteria for AFE were stratified into cardiopulmonary collapse-type AFE and disseminated intravascular coagulation (DIC)-type AFE groups. The relationship between blood loss and fibrinogen at onset was examined to compare DIC severity. Vital signs at onset were not significantly different. The AFE group had significantly less blood loss at onset (1506 mL vs 1843 mL, P = 0.0163), significantly more blood loss 2 h post-onset (3304 mL vs 1996 mL, P < 0.0001) and more severe coagulopathy and fibrinolysis. The blood loss/fibrinogen (B/F) ratio at onset was significantly higher in the DIC-type AFE group (23.15 ± 8.07 vs 6.28 ± 3.35 mL dL/mg, P < 0.0001). AFE was complicated by catastrophic DIC irrespective of blood loss at onset. Fibrinogen exhibited the strongest correlation among test findings at onset. The B/F ratio may help differentiate PPH from DIC-type AFE and diagnose clinical AFE, facilitating optimal replacement of coagulation factors during the early stages.

Differences of maternal mortality rate between Shanghai and New York city from the perspective of regulatory policy

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Background

Regulatory policy (RP) is known as a major factor to improve health care system performance. A significant difference in maternal mortality rates (MMRs) was observed between New York city (NYC) and Shanghai (SH), both first-class international metropolises. This study aims to adopt a quantitative evaluation model to analyze whether RP differences contribute to the different MMRs of the two cities.

Methods

Based on collection of all publicly released policy documents regarding maternal health in the two cities, we assessed and compared the status of their maternal health care RPs from 2006 to 2017 through a series of quantitative indicators as regulatory elements coverage rate (RECR), departmental responsibility clarity rate (DRCR), and accountability mechanism clarity rate (AMCR), based on two characteristics of comprehensiveness and effectiveness of RPs. Pearson correlation analysis, principal component analysis, and linear regression analysis were used to test the relationships between the indicators and MMR in SH and NYC.

Results

By 2017, disparities of maternal health care RP are found between SH and NYC, from the indicators of RECR (100% vs. 77.0%), DRCR (38.9% vs. 45.1%), and AMCR (29.2% vs. 22.5%). From 2006 to 2017, RECR, DRCR, and AMCR in SH have shown a higher growth of 8.7%, 53.2%, and 45.2%, compared with growth of 25.0%, 12.5%, and 2.9% in NYC. The three indicators were found all negatively correlated with MMR in SH (Coefficients = −0.831, −0.833, and −0.909, and P < 0.01), while only RECR and DRCR had negative correlation with MMR in NYC (Coefficients = −0.736 and −0.683, and P < 0.05). Linear regression showed that the principal components of the three indicators were found with significant impact on MMRs both in SH (R = 0.914, R² = 0.836, P < 0.001) and NYC (R = 0.854, R² = 0.357, P = 0.04).

Conclusion

Compared with NYC, the more comprehensive and effective maternal health care RPs in SH had a stronger impact on MMR control, which contributed to the differences between the two cities’ MMRs to some extent. The methods and indicators we adopted for assessment are reasonable and comparable.

Amniotic fluid embolism and management of coagulopathy: A case report with successful outcome

Amniotic fluid embolism (AFE) is a rare and potentially catastrophic condition unique to pregnancy. Presentation may range from subtle clinical events to sudden and fatal maternal cardiorespiratory arrest, with a reported incidence of 2–6 in 100,000 deliveries and mortality of 15–60%. Management should include immediate high-grade resuscitation for AFE presenting as cardiac arrest, involvement of multidisciplinary team, provision of adequate ventilator and circulatory support, treatment of coagulopathy precipitated by AFE, and immediate delivery of the foetus in cases of cardiac arrest. The following case report involves a patient with suspected AFE post-induction of labour with favourable maternal and neonatal outcome in our local setting. The management of coagulopathy in AFE is further discussed, including use of massive transfusion protocols, pharmacological agents and recombinant factor VIIa.

The Impact of Severe Maternal Morbidity on Perinatal Outcomes in High Income Countries: Systematic Review and Meta-Analysis

While there is clear evidence that severe maternal morbidity (SMM) contributes significantly to poor maternal health outcomes, limited data exist on its impact on perinatal outcomes. We undertook a systematic review and meta-analysis to ascertain the association between SMM and adverse perinatal outcomes in high-income countries (HICs). We searched for full-text publications in PubMed, Embase, Cumulative Index of Nursing and Allied Health Literature (CINAHL), and Scopus databases. Studies that reported data on the association of SMM and adverse perinatal outcomes, either as a composite or individual outcome, were included. Two authors independently assessed study eligibility, extracted data, and performed quality assessment using the Newcastle-Ottawa Scale. We used random-effects modelling to calculate odds ratios (ORs) with 95% confidence intervals. We also assessed the risk of publication bias and statistical heterogeneity using funnel plots and Higgins I2, respectively. We defined sub-groups of SMM as hemorrhagic disorders, hypertensive disorders, cardiovascular disorders, hepatic disorders, renal disorders, and thromboembolic disorders. Adverse perinatal outcome was defined as preterm birth (before 37 weeks gestation), small for gestational age (SGA) (birth weight (BW) < 10th centile for gestation), low birthweight (LBW) (BW < 2.5 kg), Apgar score < 7 at 5 min, neonatal intensive care unit (NICU) admission, stillbirth and perinatal death (stillbirth and neonatal deaths up to 28 days). A total of 35 studies consisting of 38,909,426 women were included in the final analysis. SMMs associated with obstetric hemorrhage (OR 3.42, 95% CI: 2.55-4.58), severe hypertensive disorders (OR 6.79, 95% CI: 6.06-7.60), hepatic (OR 3.19, 95% CI: 2.46-4.13) and thromboembolic disorders (OR 2.40, 95% CI: 1.67-3.46) were significantly associated with preterm birth. SMMs from hypertensive disorders (OR 2.86, 95% CI: 2.51-3.25) or thromboembolic disorders (OR 1.48, 95% CI: 1.09-1.99) were associated with greater odds of having SGA infant. Women with severe hemorrhage had increased odds of LBW infant (OR 2.31, 95% CI: 1.57-3.40). SMMs from obstetric hemorrhage (OR 4.16, 95% CI: 2.54-6.81) or hypertensive disorders (OR 4.61, 95% CI: 1.17-18.20) were associated with an increased odds of low 5-min Apgar score and NICU admission (Severe obstetric hemorrhage: OR 3.34, 95% CI: 2.26-4.94 and hypertensive disorders: OR 3.63, 95% CI: 2.63-5.02, respectively). Overall, women with SMM were 4 times more likely to experience stillbirth (OR 3.98, 95%C 3.12-7.60) compared to those without SMM with cardiovascular disease (OR 15.2, 95% CI: 1.29-180.60) and thromboembolic disorders (OR 9.43, 95% CI: 4.38-20.29) conferring greatest risk of this complication. The odds of neonatal death were significantly higher in women with SMM (OR 3.98, 95% CI: 2.44-6.47), with those experiencing hemorrhagic (OR 7.33, 95% CI: 3.06-17.53) and hypertensive complications (OR 3.0, 95% CI: 1.78-5.07) at highest risk. Overall, SMM was also associated with higher odds of perinatal death (OR 4.74, 95% CI: 2.47-9.12) mainly driven by the increased risk in women experiencing severe obstetric hemorrhage (OR 6.18, 95% CI: 2.55-14.96). Our results highlight the importance of mitigating the impact of SMM not only to improve maternal health but also to ameliorate its consequences on perinatal outcomes.

Extracorporeal Therapies for Amniotic Fluid Embolism

BACKGROUND

Amniotic fluid embolism (AFE) is a catastrophic disease with significant mortality. Because the cardiopulmonary dysfunction associated with AFE is self-limited, the disease could be well suited to the use of extracorporeal therapies.

CASE

A woman progressed into cardiac arrest immediately after an elective cesarean delivery. Owing to severe hypoxemia and hypotension, AFE was suspected and peripheral venoarterial extracorporeal membrane oxygenation was quickly initiated. Subsequent evolution was complicated by intrabdominal bleeding, which required massive transfusion and multiple surgeries. The patient recovered well, with a healthy newborn. We have identified 19 similar cases in the literature and present their outcomes as a series.

CONCLUSION

Extracorporeal therapies can support severely ill women affected by AFE and could be considered even in the presence of disseminated intravascular coagulation and bleeding.

Venoarterial Extracorporeal Membrane Oxygenation as Supportive Therapy After Cardiac Arrest After Amniotic Fluid Embolism: A Case Report

Amniotic fluid embolism is a rare but dreaded complication of pregnancy, with an incidence between 2 and 7/100,000 deliveries. We report an amniotic fluid embolism after urgent cesarean delivery diagnosed on a cardiac arrest, complicated by cardiogenic shock and acute respiratory distress syndrome. This report describes the indication, efficacy, and success of venoarterial extracorporeal membrane oxygenation in the early management of cardiac arrest, cardiac failure driven by amniotic fluid embolism, and acute respiratory distress syndrome. The use of venoarterial extracorporeal membrane oxygenation support after recovery from cardiac arrest after amniotic fluid embolism should be considered early during the management of these cases.

Pulmonary amniotic fluid embolism in a rhesus macaque (Macaca mulatta)

A pregnant female rhesus macaque died spontaneously during stage two labor. Gross and histopathologic findings included severe pulmonary edema, with low numbers of blood vessels containing pale basophilic mucinous material (Alcian Blue positive and PTAH negative), consistent with intravascular amniotic fluid-derived mucin resulting in pulmonary amniotic fluid embolism.

Anesthetic management of amniotic fluid embolism -- a multi-center, retrospective, cohort study

INTRODUCTION

Amniotic fluid embolism (AFE) is a rare and potentially lethal obstetric complication, commonly occurring during labor, delivery, or immediately postpartum. There is a paucity of data regarding incidence, risk factors, and clinical management. Our primary objective in this study was to evaluate clinical presentation of AFE and delineate anesthesia management of these cases.

METHODS

This 10 years retrospective multi-center cohort study was performed in five tertiary university-affiliated medical centers, between the years 2005 and 2015. All documented cases of AFE identified according to the ICD guidelines were reviewed manually to determine eligibility for AFE according to Clark's criteria. All cases confirming Clark's diagnosis were included in the cohort.

RESULTS

Throughout the study period, 20 cases of AFE were identified, with an incidence of 4.1 per 100,000 births. Average age at presentation was 35 ± 5 years. Seventy percent of cases presented during vaginal delivery, 20% occurred throughout a cesarean delivery, and 10% occurred during a dilation and evacuation procedure. The most common presenting symptom was sudden loss of consciousness in 12 parturients (66.7%), fetal bradycardia in 11 parturients (55%), and shortness of breath in 10 parturients (50%). Perimortem cesarean section was performed in 55% of cases, although only one case was performed in the delivery suite, while all others were performed in the operating room. Echocardiography was performed in 60% of the cases and all were pathological. Furthermore, 20% of cases were connected to an extracorporeal membrane oxygenation machine. There was a 15% mortality rate of 15%. A further 15% suffered major neurological disability, 25% suffered minor neurological morbidity, and 45% survived without severe complications.

CONCLUSION

AFE is associated with significant maternal morbidity. This study highlights the importance of providing advanced training for the delivery suite staff for cases of maternal cardiovascular collapse secondary to AFE and increasing awareness for this rare and devastating obstetric condition.

Amniotic fluid embolism mortality rate

AIM

The objective of this study was to determine the mortality rate of amniotic fluid embolism (AFE) using population-based studies and case series.

METHODS

A literature search was conducted using the two key words: 'amniotic fluid embolism (AFE)' AND 'mortality rate'. Thirteen population-based studies were evaluated, as well as 36 case series including at least two patients.

RESULTS

The mortality rate from population-based studies varied from 11% to 44%. When nine population-based studies with over 17 000 000 live births were aggregated, the maternal mortality rate was 20.4%. In contrast, the mortality rate of AFE in case series varies from 0% to 100% with numerous rates in between.

CONCLUSION

The AFE mortality rate in population-based studies varied from 11% to 44% with the best available evidence supporting an overall mortality rate of 20.4%. Data from case series should no longer be used as a basis for describing the lethality of AFE.

Improving hospital quality to reduce disparities in severe maternal morbidity and mortality

Significant racial/ethnic disparities in maternal morbidity and mortality exist in the United States. Black women are 3-4 times more likely to die a pregnancy-related death as compared with white women. Growing research suggests that hospital quality may be a critical lever for improving outcomes and narrowing disparities. This overview reviews the evidence demonstrating that hospital quality is related to maternal mortality and morbidity, discusses the pathways through which these associations between quality and severe maternal morbidity generate disparities, and concludes with a discussion of possible levers for action to reduce disparities by improving hospital quality.

Amniotic Fluid Embolism. Is a New Pregnancy Possible? Case Report

Amniotic fluid embolism (AFE) is a rare but potentially catastrophic clinical condition, characterized by a combination of signs and symptoms that reflect respiratory distress, cardiovascular collapse and disseminated intravascular coagulation (DIC). Its pathogenesis is still unclear. More recently, the traditional view of obstruction of pulmonary capillary vessels by amniotic fluid emboli as the main explanation for the etiology has been ruled out, and immunologic factors and the activation of the inflammatory cascade took on an important role. Amniotic fluid embolism has an unpredictable character, its diagnosis is exclusively clinical, and the treatment consists mainly of cardiovascular support and administration of blood products to correct the DIC. No diagnostic test is recommended until now, though multiple blood markers are currently being studied. The authors present a case report of a woman who had survived AFE in her previous pregnancy and had a subsequent pregnancy without recurrence, providing one more clinical testimony of the low risks for the pregnancy after AFE.

Site of delivery contribution to black-white severe maternal morbidity disparity

BACKGROUND

The black-white maternal mortality disparity is the largest disparity among all conventional population perinatal health measures, and the mortality gap between black and white women in New York City has nearly doubled in recent years. For every maternal death, 100 women experience severe maternal morbidity, a life-threatening diagnosis, or undergo a life-saving procedure during their delivery hospitalization. Like maternal mortality, severe maternal morbidity is more common among black than white women. A significant portion of maternal morbidity and mortality is preventable, making quality of care in hospitals a critical lever for improving outcomes. Hospital variation in risk-adjusted severe maternal morbidity rates exists. The extent to which variation in hospital performance on severe maternal morbidity rates contributes to black-white disparities in New York City hospitals has not been studied.

OBJECTIVE

We examined the extent to which black-white differences in severe maternal morbidity rates in New York City hospitals can be explained by differences in the hospitals in which black and white women deliver.

STUDY DESIGN

We conducted a population-based study using linked 2011-2013 New York City discharge and birth certificate datasets (n = 353,773 deliveries) to examine black-white differences in severe maternal morbidity rates in New York City hospitals. A mixed-effects logistic regression with a random hospital-specific intercept was used to generate risk-standardized severe maternal morbidity rates for each hospital (n = 40). We then assessed differences in the distributions of black and white deliveries among these hospitals.

RESULTS

Severe maternal morbidity occurred in 8882 deliveries (2.5%) and was higher among black than white women (4.2% vs 1.5%, P < .001). After adjustment for patient characteristics and comorbidities, the risk remained elevated for black women (odds ratio, 2.02; 95% confidence interval, 1.89-2.17). Risk-standardized severe maternal morbidity rates among New York City hospitals ranged from 0.8 to 5.7 per 100 deliveries. White deliveries were more likely to be delivered in low-morbidity hospitals: 65% of white vs 23% of black deliveries occurred in hospitals in the lowest tertile for morbidity. We estimated that black-white differences in delivery location may contribute as much as 47.7% of the racial disparity in severe maternal morbidity rates in New York City.

CONCLUSION

Black mothers are more likely to deliver at higher risk-standardized severe maternal morbidity hospitals than are white mothers, contributing to black-white disparities. More research is needed to understand the attributes of high-performing hospitals and to share best practices among hospitals.

Amniotic fluid embolism: diagnosis and management

OBJECTIVE

We sought to provide evidence-based guidelines regarding the diagnosis and management of amniotic fluid embolism.

STUDY DESIGN

A systematic literature review was performed using MEDLINE, PubMed, EMBASE, and the Cochrane Library. The search was restricted to English-language articles published from 1966 through March 2015. Priority was given to articles reporting original research, in particular randomized controlled trials, although review articles and commentaries were consulted. Abstracts of research presented at symposia and scientific conferences were not considered adequate for inclusion. Evidence reports and published guidelines were also reviewed, and additional studies were located by reviewing bibliographies of identified articles. Grading of Recommendations Assessment, Development, and Evaluation (GRADE) methodology was used for defining the strength of recommendations and rating quality of the evidence. Consistent with US Preventive Task Force guidelines, references were evaluated for quality based on the highest level of evidence.

RESULTS AND RECOMMENDATIONS

We recommend the following: (1) we recommend consideration of amniotic fluid embolism in the differential diagnosis of sudden cardiorespiratory collapse in the laboring or recently delivered woman (GRADE 1C); (2) we do not recommend the use of any specific diagnostic laboratory test to either confirm or refute the diagnosis of amniotic fluid embolism; at the present time, amniotic fluid embolism remains a clinical diagnosis (GRADE 1C); (3) we recommend the provision of immediate high-quality cardiopulmonary resuscitation with standard basic cardiac life support and advanced cardiac life support protocols in patients who develop cardiac arrest associated with amniotic fluid embolism (GRADE 1C); (4) we recommend that a multidisciplinary team including anesthesia, respiratory therapy, critical care, and maternal-fetal medicine should be involved in the ongoing care of women with AFE (Best Practice); (5) following cardiac arrest with amniotic fluid embolism, we recommend immediate delivery in the presence of a fetus ≥23 weeks of gestation (GRADE 2C); (6) we recommend the provision of adequate oxygenation and ventilation and, when indicated by hemodynamic status, the use of vasopressors and inotropic agents in the initial management of amniotic fluid embolism. Excessive fluid administration should be avoided (GRADE 1C); and (7) because coagulopathy may follow cardiovascular collapse with amniotic fluid embolism, we recommend the early assessment of clotting status and early aggressive management of clinical bleeding with standard massive transfusion protocols (GRADE 1C).

Disseminated Intravascular Coagulation Syndromes in Obstetrics

Disseminated intravascular coagulation (DIC) is a syndrome that can be initiated by a myriad of medical, surgical, and obstetric disorders. Also known as consumptive coagulopathy, DIC is a common contributor to maternal morbidity and mortality and is associated with up to 25% of maternal deaths. The etiopathogenesis of DIC is complex and currently thought to be initiated by tissue factor or thromboplastin, which is released from trophoblastic or fetal tissue, or maternal decidua or endothelium. Tissue factor activates the coagulation sequence to cause fibrin clotting and its dissolution by the fibrinolysin system. The result of this process can range from mild, clinically insignificant laboratory derangements to marked coagulopathy with bleeding at sites of minimal trauma. Although clinical recognition varies by disease severity, several organizations have attempted to standardize the diagnosis through development of scoring systems. Several important--albeit not necessarily common--obstetric disorders associated with DIC include placental abruption, amniotic fluid embolism, sepsis syndrome, and acute fatty liver of pregnancy. More common disorders include severe preeclampsia, hemolysis, elevated liver enzymes, and low platelet count syndrome, and massive obstetric hemorrhage. Importantly, many of these disorders either cause or are associated with substantive obstetric hemorrhage. Treatment of DIC is centered on two principles. The first is identification and treatment of the underlying disorder. Because many women with consumptive coagulopathy also have massive hemorrhage, the second tenet of treatment is that obstetric complications such as uterine atony or lacerations must be controlled simultaneously with prompt blood and component replacement for a salutary outcome.

Acute respiratory failure and mechanical ventilation in pregnant patient: A narrative review of literature

Physiological changes of pregnancy imposes higher risk of acute respiratory failure (ARF) with even a slight insult and remains an important cause of maternal and fetal morbidity and mortality. Although pregnant women have different respiratory physiology and different causes of ARF, guidelines specific to ventilatory settings, goals of oxygenation and weaning process could not be framed due to lack of large-scale randomized controlled trials. During the 2009 H1N1 pandemic, pregnant women had higher morbidity and mortality compared to nonpregnant women. During this period, alternative strategies of ventilation such as high-frequency oscillatory ventilation, inhalational of nitric oxide, prone positioning, and extra corporeal membrane oxygenation were increasingly used as a desperate measure to rescue pregnant patients with severe hypoxemia who were not improving with conventional mechanical ventilation. This article highlights the causes of ARF and recent advances in invasive, noninvasive and alternative strategies of ventilation used during pregnancy.

Amniotic fluid embolism: an Australian-New Zealand population-based study

Background

Amniotic fluid embolism (AFE) is a major cause of direct maternal mortality in Australia and New Zealand. There has been no national population study of AFE in either country. The aim of this study was to estimate the incidence of amniotic fluid embolism in Australia and New Zealand and to describe risk factors, management, and perinatal outcomes.

Methods

A population-based descriptive study using the Australasian Maternity Outcomes Surveillance System (AMOSS) carried out in 263 eligible sites (>50 births per year) covering an estimated 96 % of women giving birth in Australia and all 24 New Zealand maternity units (100 % of women giving birth in hospitals) between January 1 2010-December 31 2011. A case of AFE was defined either as a clinical diagnosis (acute hypotension or cardiac arrest, acute hypoxia and coagulopathy in the absence of any other potential explanation for the symptoms and signs observed) or as a post mortem diagnosis (presence of fetal squames/debris in the pulmonary circulation).

Results

Thirty-three cases of AFE were reported from an estimated cohort of 613,731women giving birth, with an estimated incidence of 5.4 cases per 100 000 women giving birth (95 % CI 3.5 to 7.2 per 100 000). Two (6 %) events occurred at home whilst 46 % (n = 15) occurred in the birth suite and 46 % (n = 15) in the operating theatre (location not reported in one case). Fourteen women (42 %) underwent either an induction or augmentation of labour and 22 (67 %) underwent a caesarean section. Eight women (24 %) conceived using assisted reproduction technology.

Thirteen (42 %) women required cardiopulmonary resuscitation, 18 % (n = 6) had a hysterectomy and 85 % (n = 28) received a transfusion of blood or blood products. Twenty (61 %) were admitted to an Intensive Care Unit (ICU), eight (24 %) were admitted to a High Dependency Unit (HDU) and seven (21 %) were transferred to another hospital for further management. Five woman died (case fatality rate 15 %) giving an estimated maternal mortality rate due to AFE of 0.8 per 100 000 women giving birth (95 % CI 0.1 % to 1.5 %). There were two deaths among 36 infants.

Conclusions

A coordinated emergency response requiring resource intense multi-disciplinary input is required in the management of women with AFE. Although the case fatality rate is lower than in previously published studies, high rates of hysterectomy, resuscitation, and admission to higher care settings reflect the significant morbidity associated with AFE. Active, ongoing surveillance to document the risk factors and short and long-term outcomes of women and their babies following AFE may be helpful to guide best practice, management, counselling and service planning. A potential link between AFE and assisted reproductive technology warrants further investigation.

ARDS in pregnancy

Acute respiratory distress syndrome (ARDS) is an uncommon condition in pregnant patients. The causes of ARDS are associated with obstetric causes such as amniotic fluid embolism, preeclampsia, septic abortion, and retained products of conception or nonobstetric causes that include sepsis, aspiration pneumonitis, influenza pneumonia, blood transfusions, and trauma. An essential component in management of ARDS involves good communication between the obstetrics team and critical care specialist and a fundamental understanding of mechanical ventilatory support. Medical therapies such as nitric oxide and corticosteroids play a complimentary role. Extracorporeal life support is beneficial in the management of the parturient with severe ARDS.

Impact of pre-pregnancy diabetes mellitus on congenital anomalies, Canada, 2002-2012

OBJECTIVE

To examine the impact of pre-pregnancy diabetes mellitus (DM) on the population birth prevalence of congenital anomalies in Canada.

METHODS

We carried out a population-based study of all women who delivered in Canadian hospitals (except those in the province of Quebec) between April 2002 and March 2013 and their live-born infants with a birth weight of 500 grams or more and/or a gestational age of 22 weeks or more. Pre-pregnancy type 1 or type 2 DM was identified using ICD-10 diagnostic codes. The association between DM and all congenital anomalies as well as specific congenital anomaly categories was estimated using adjusted odds ratios; the impact was calculated as a population attributable risk percent (PAR%).

RESULTS

There were 118,892 infants with a congenital anomaly among 2,839,680 live births (41.9 per 1000). While the prevalence of any congenital anomaly declined from 50.7 per 1000 live births in 2002/03 to 41.5 per 1000 in 2012/13, the corresponding PAR% for a congenital anomaly related to pre-pregnancy DM rose from 0.6% (95% confidence interval [CI]: 0.4-0.8) to 1.2% (95% CI: 0.9-1.4). Specifically, the PAR% for congenital cardiovascular defects increased from 2.3% (95% CI: 1.7-2.9) to 4.2% (95% CI: 3.5-4.9) and for gastrointestinal defects from 0.8% (95% CI: 0.2-1.9) to 1.4% (95% CI: 0.7-2.6) over the study period.

CONCLUSION

Although there has been a relative decline in the prevalence of congenital anomalies in Canada, the proportion of congenital anomalies due to maternal pre-pregnancy DM has increased. Enhancement of preconception care initiatives for women with DM is recommended.

Amniotic fluid embolism pathophysiology suggests the new diagnostic armamentarium: β-tryptase and complement fractions C3-C4 are the indispensable working tools

Amniotic fluid embolism (AFE) is an uncommon obstetric condition involving pregnant women during labor or in the initial stages after delivery. Its incidence is estimated to be around 5.5 cases per 100,000 deliveries. Therefore, this paper investigated the pathophysiological mechanism, which underlies AFE, in order to evaluate the role of immune response in the development of this still enigmatic clinical entity. The following databases (from 1956 to September 2014) Medline, Cochrane Central, Scopus, Web of Science and Science Direct were used, searching the following key words: AFE, pathophysiology, immune/inflammatory response, complement and anaphylaxis. The main key word “AFE” was searched singularly and associated individually to each of the other keywords. Of the 146 sources found, only 19 were considered appropriate for the purpose of this paper. The clinical course is characterized by a rapid onset of symptoms, which include: acute hypotension and/or cardiac arrest, acute hypoxia (with dyspnoea, cyanosis and/or respiratory arrest), coagulopathies (disseminated intravascular coagulation and/or severe hemorrhage), coma and seizures. The pathology still determines a significant morbidity and mortality and potential permanent neurological sequelae for surviving patients. At this moment, numerous aspects involving the pathophysiology and clinical development are still not understood and several hypotheses have been formulated, in particular the possible role of anaphylaxis and complement. Moreover, the detection of serum tryptase and complement components and the evaluation of fetal antigens can explain several aspects of immune response.

Fetuses-at-risk, to avoid paradoxical associations at early gestational ages: extension to preterm infant mortality

BACKGROUND

Fetuses-at-risk denominators are commonly used in research on preterm stillbirth, but applications to postnatal outcomes such as preterm infant mortality are controversial. We evaluated whether biased associations between maternal risk factors and preterm infant mortality caused by stratification by preterm birth could be avoided using fetuses-at-risk risk ratios.

METHODS

Data included 3 277 570 births drawn from the linked live birth-death file for Canada from 1990 through 2005. We used maternal age as the risk factor, and estimated the association with stillbirth, early neonatal, late neonatal and postneonatal mortality by gestational interval (22-24, 25-27, 28-31, 32-36, ≥37 weeks). Models were run using (i) log-binomial regression stratified by preterm gestational age, and (ii) unstratified log-binomial regression using fetuses-at-risk denominators.

RESULTS

Extremes of maternal age were associated with higher mortality among term births. Among preterm births, the stratified model suggested a protective, null or attenuated association of extremes of maternal age with stillbirth, early, late and post neonatal mortality. The unstratified fetuses-at-risk model, however, resulted in the expected higher risk of mortality at extremes of maternal age for all outcomes.

CONCLUSIONS

Fetuses-at-risk regression can avoid paradoxical associations between maternal exposures and mortality of infants born early in gestation, caused by preterm birth stratification bias. The fetuses-at-risk approach can be extended through the first year of life, or potentially beyond, depending on the outcome and presence of unmeasured confounders associated with preterm birth.

Amniotic Fluid Embolism (AFE) in China: Are maternal mortality and morbidity preventable?

A case of hospital-patient conflict has occurred in China that has lifted billows in the public and highlighted the lethality of amniotic fluid embolism (AFE). AFE is a rare but severe obstetric complication with high maternal mortality and morbidity. Globally, the incidence of AFE is estimated to be approximately 2 to 6 per 100,000 deliveries. The maternal mortality rate (MMR) attributable to AFE ranges between 0.5 to 1.7 deaths per 100,000 deliveries in the developed world and 1.9 to 5.9 deaths per 100,000 deliveries in the developing world. In developed countries, AFE often accounts for a leading cause of maternal mortality; whereas the proportion of maternal death caused by AFE tends to be not as dominant compared to common perinatal complications in developing countries. With the mechanism remaining to be elucidated, AFE can neither be predicted nor prevented even in developed countries. Treatment requires a set of highly intensive advanced emergency obstetric care, challenging obstetric care in developing countries. Although this complication is currently far from preventable, China has potential to improve the prognosis of AFE by strengthening the emergency obstetric care system.

Incidence, diagnosis and pathophysiology of amniotic fluid embolism

Amniotic fluid embolism (AFE) is a rare clinical entity, sometimes fatal. A review was conducted to describe the frequency, diagnosis and pathophysiology of AFE. The reported incidences ranged from 1.9 cases per 100,000 maternities (UK) to 6.1 per 100,000 maternities (Australia), which can vary considerably, depending on the period, region of study and the definition. Although the development of amniotic fluid-specific markers would have an impact on early diagnosis, definition of AFE based on these markers is not widely accepted. To date, immunological mechanisms, amniotic fluid-dependent anaphylactic reaction and complement activation, have been proposed as potential pathogenetic and pathophysiological mechanisms. Immune cell activation induced through complement activation may be associated with the mechanism that immediately initiates maternal death, only in susceptible individuals. This review will focus on advances in the field of AFE biology and discuss the prevalence, diagnosis and pathophysiology of AFE.

Amniotic fluid embolism: an interdisciplinary challenge: epidemiology, diagnosis and treatment

BACKGROUND

Amniotic fluid embolism (AFE) is a life-threatening obstetric complication that arises in 2 to 8 of every 100 000 deliveries. With a mortality of 11% to 44%, it is among the leading direct causes of maternal death. This entity is an interdisciplinary challenge because of its presentation with sudden cardiac arrest without any immediately obvious cause, the lack of specific diagnostic tests, the difficulty of establishing the diagnosis and excluding competing diagnoses, and the complex treatment required, including cardio - pulmonary resuscitation.

METHOD

We selectively reviewed pertinent literature published from 2000 to May 2013 that was retrieved by a PubMed search.

RESULTS

The identified risk factors for AFE are maternal age 35 and above (odds ratio [OR] 1.86), Cesarean section (OR 12.4), placenta previa (OR 10.5), and multiple pregnancy (OR 8.5). AFE is diagnosed on clinical grounds after the exclusion of other causes of acute cardiovascular decompensation during delivery, such as pulmonary thromboembolism or myocardial infarction. Its main clinical features are severe hypotension, arrhythmia, cardiac arrest, pulmonary and neurological manifestations, and profuse bleeding because of disseminated intravascular coagulation and/or hyperfibrinolysis. Its treatment requires immediate, optimal interdisciplinary cooperation. Low-level evidence favors treating women suffering from AFE by securing the airway, adequate oxygenation, circulatory support, and correction of hemostatic disturbances. The sudden, unexplained death of a pregnant woman necessitates a forensic autopsy. The histological or immunohistochemical demonstration of formed amniotic fluid components in the pulmonary bloodflow establishes the diagnosis of AFE.

CONCLUSION

AFE has become more common in recent years, for unclear reasons. Rapid diagnosis and immediate interdisciplinary treatment are essential for a good outcome. Establishing evidence-based recommendations for intervention is an important goal for the near future.

Incidence, risk factors, and consequences of amniotic fluid embolism

BACKGROUND

Amniotic fluid embolism (AFE) is a rare but serious cause of maternal mortality whose aetiology remains obscure. Previous population-based studies have reported associations with labour induction and caesarean delivery.

METHODS

We updated a previous analysis based on the US Nationwide Inpatient Sample from 1999 to 2008. We adapted a diagnostic validation algorithm to minimise false-positive diagnoses, along with statistical methods that account for the stratified random sampling design.

RESULTS

Of the 8 571 209 deliveries recorded in the database, 276 met our case definition of AFE, of which 62 (22.9% of the 274 with known vital status) were fatal. Significant associations with AFE were observed for medical induction {adjusted odds ratio [aOR] = 1.7 [95% confidence interval (CI) 1.2, 2.5]}, caesarean delivery [aOR = 15.0; 95% CI 9.4, 23.9], instrumental vaginal delivery [aOR = 6.6; 95% CI 4.0, 11.1], and cervical/uterine trauma [aOR = 7.4; 95% CI 3.6, 14.9]. AFE was associated with increases in risk of stillbirth, hysterectomy, maternal death, and prolonged maternal length of delivery hospital stay.

CONCLUSIONS

AFE remains an extremely serious obstetric complication with high risks of maternal and fetal mortality. The increased risks of AFE associated with labour induction and caesarean delivery have implications for elective use of these interventions.