Association of Pregnancy Characteristics and Maternal Mortality With Amniotic Fluid Embolism

Abstract

ImportanceAmniotic fluid embolism (AFE) is an uncommon pregnancy complication but is associated with high maternal mortality. Because of the rarity of AFE, associated risks factors and maternal outcomes have been relatively understudied.ObjectiveTo examine the clinical, pregnancy, and delivery characteristics and the maternal outcomes related to AFE in a recent period in the US.Design, Setting, and ParticipantsThis retrospective cohort study examined hospital deliveries from January 1, 2016, to December 31, 2019, from the Healthcare Cost and Utilization Project’s National Inpatient Sample.Main Outcomes and MeasuresThe primary outcome was clinical, pregnancy, and delivery characteristics of AFE, assessed with a multivariable binary logistic regression model. The coprimary outcome was failure to rescue, defined as maternal mortality after AFE. Associations with other severe maternal morbidity indicators and failure to rescue per clinical and pregnancy characteristics were also assessed.ResultsA total of 14 684 135 deliveries were examined, with AFE diagnosed in 880 women, corresponding to an incidence rate of 6.0 per 100 000 deliveries. The cohort-level median patient age was 29 years (IQR, 25-33 years). In a multivariable analysis, (1) patient factors of older age, Asian and Black race, Western US region, pregestational hypertension, asthma, illicit substance use, and grand multiparity; (2) pregnancy factors of placental accreta spectrum (PAS), placental abruption, uterine rupture, polyhydramnios, chorioamnionitis, preeclampsia, fetal growth restriction, and fetal demise; and (3) delivery factors of early gestational age, cervical ripening, cesarean delivery, operative delivery, and manual removal were associated with AFE. Among these characteristics, PAS had the largest association with AFE (adjusted odds ratio [aOR], 10.01; 95% CI, 7.03-14.24). When stratified by the PAS subtypes, more severe forms of PAS had a greater association with AFE (aOR for increta and percreta, 17.35; 95% CI, 10.21-28.48; and aOR for accreta, 7.62; 95% CI, 4.83-12.01). Patients who had AFE were more likely to have coagulopathy (aOR, 24.68; 95% CI, 19.38-31.44), cardiac arrest (aOR, 24.56; 95% CI, 17.84-33.81), and adult respiratory distress syndrome (aOR, 10.72; 95% CI, 8.09-14.20). The failure-to-rescue rate after AFE was 17.0% overall. However, the failure-to-rescue rate exceeded 30% when AFE co-occurred with other severe maternal morbidity indicators: 45.8% for AFE, cardiac arrest, and coagulopathy; 43.2% for AFE, shock, and cardiac rhythm conversion; and 38.6% for AFE, cardiac arrest, coagulopathy, and shock. The failure-to-rescue rate after AFE also exceeded 30% when AFE occurred in the setting of placental pathology: 42.9% for AFE and PAS and 31.3% for AFE and placental abruption.Conclusions and RelevanceThis contemporaneous, national-level analysis validated previously known risk factors for AFE and confirmed the dismal outcomes of pregnancy complicated by AFE. The association between PAS and AFE, which was not previously reported, warrants further investigation.

Toward Risk Assessment for Amniotic Fluid Embolisms

“…The study by Mazza and colleagues assessed pregnancy characteristics, risk factors, and maternal mortality of amniotic fluid embolism (AFE), analyzing a sizeable cohort that encompasses the national US inpatient population during a 3-year period with almost 15 million deliveries and 880 cases of AFE. The estimated incidence of AFE was 6 per 100 000 deliveries, with a slight yet significant increase during the study period.…”

“…Given the rarity, poor biological understanding, and major clinical consequences of AFE, research is particularly necessary. The study by Mazza et al1 clearly shows that both the risk of AFE and the failure to recover after AFE are increasing from baseline to cases with more frequent and complex risk factors, with an interesting and statistically significant progression.The finding of PAS as a risk factor for AFE supports a pathogenetic role for the breakdown of the maternal-fetal barrier with increased exposure of fetal or trophoblastic constituents in the maternal circulation. Future studies may explore in this light the extent and characteristics of fetal or trophoblastic material in the maternal blood of patients with PAS or AFE compared with healthy pregnant patients.…”

“…Given the rarity, poor biological understanding, and major clinical consequences of AFE, research is particularly necessary. The study by Mazza et al clearly shows that both the risk of AFE and the failure to recover after AFE are increasing from baseline to cases with more frequent and complex risk factors, with an interesting and statistically significant progression.…”

Trends, Characteristics, and Maternal Morbidity Associated With Unhoused Status in Pregnancy

“…Identification of these covariates was based on the Diagnosis-Related Group, ICD-10-CM, and ICD-10 Procedure Coding System codes (eTable 1 in Supplement 1). The covariates were grouped similarly in prior studies …”

Extracorporeal Cardiopulmonary Resuscitation for Amniotic Fluid Embolism

“…The pathophysiology of AFE includes an inflammatory and coagulopathic response due to fetal materials entering maternal circulation (Viau-Lapointe & Filewod, 2019). In the United States, based on data from the National Inpatient Sample of 14.6 million hospital births from 2016 to 2019, the incidence of AFE was 6 in 100,000 births (Mazza et al, 2022). Maternal mortality due to AFE has been found to be between 10% and 17% and neonatal mortality ~6% (Mazza et al, 2022; Stafford et al, 2020).…”