Incidence and risk factors of amniotic fluid embolisms: a population-based study on 3 million births in the United States.
OBJECTIVE
Amniotic fluid embolism (AFE) is a condition occurring during delivery that can lead to severe maternal morbidity and mortality. Given the rarity of its occurrence, current estimates and predictors of the incidence and outcomes are often difficult to obtain.


METHODS
We conducted a population-based cohort study on 3 million birth records in the Healthcare Cost and Utilization Project-Nationwide Inpatient Sample from 1999 to 2003 to estimate the incidence and case fatality of AFEs. Logistic regression was used to calculate the odds ratio (OR) and corresponding 95% confidence intervals (CIs) of demographic and obstetrical determinants of AFEs and fatal AFEs.


RESULTS
The overall incidence of AFE was 7.7 per 100,000 births (95% CI 6.7 to 8.7), with a case fatality rate of 21.6% (95% CI 15.5 to 27.6%). AFE was associated with maternal age greater than 35 (OR 2.2, 95% CI 1.5 to 2.1), placenta previa (OR 30.4, 95% CI 15.4 to 60.1), and cesarean delivery (OR 5.7, 95% CI 3.7 to 8.7). Although AFEs were not significantly associated with induction of labor (OR 1.5, 95% CI 0.9 to 2.3), they were associated with preeclampsia, abruptio placentae, and the use of forceps. Among women with an AFE, common demographic or obstetrical determinants were not predictive of maternal mortality.


CONCLUSIONS
AFE is a rare but serious condition that is associated with advanced maternal age, placental pathologies, and cesarean deliveries. Further research on the treatment of this condition is necessary.
Abenhaim
Haim A
HA
Department of Obstetrics and Gynecology, CHU Sainte-Justine, University of Montreal, Montreal, QC, Canada. haim.abenhaim@gmail.com
Azoulay
Laurent
L
Kramer
Michael S
MS
Leduc
Line
L
D000328:Adult; D002585:Cesarean Section / Q000009:adverse effects*; D015331:Cohort Studies; D004619:Embolism, Amniotic Fluid / Q000453:epidemiology* / Q000209:etiology*; D005260:Female; D006801:Humans; D015994:Incidence; D008423:Maternal Age; D010923:Placenta Previa; D011247:Pregnancy; D011256:Pregnancy Outcome; D012307:Risk Factors; D014481:United States / Q000453:epidemiology