Incidence and risk factors of amniotic fluid embolisms: a population-based study on 3 million births in the United States

Published:February 25, 2008DOI:


      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.

      Study Design

      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.


      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.


      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.

      Key words

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      Linked Article

      • Amniotic fluid embolism: active surveillance versus retrospective database review
        American Journal of Obstetrics & GynecologyVol. 199Issue 4
        • Preview
          Abenhaim et al1 reported an incidence of amniotic fluid embolism (AFE) of 7.7 per 100,000 births in a retrospective, population-based cohort study. Both this, and other population-based studies reported in the literature,2 ascertained cases through interrogation of a coded hospital admissions database. As other authors2 point out, diagnosis of amniotic fluid embolism is difficult, and coded data may be flawed,3 thus limiting the accuracy of incidence estimates obtained from retrospective database review.
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