Incidence of amniotic fluid embolism: relation to cesarean section and to age.

AIMS: To determine the incidence of amniotic fluid embolism and the incidence as modified by cesarean section and age.

METHODS: Data are from the National Hospital Discharge Survey. We examined the number of patients discharged from short-stay nonfederal hospitals throughout the United States, from 1980 through 2005, with a diagnostic code for amniotic fluid embolism.

RESULTS: From 1980 through 2005, there were 112,712,000 deliveries, of which 12,000 patients (11/100,000) had amniotic fluid embolism. The incidence of amniotic fluid embolism was lower in 1993-2005 than in 1980-1992 (9/100,000 vs. 12/100,000)(p < 0.0001). The incidence of amniotic fluid embolism was higher with cesarean section, 5,000 of 22,937,000 (22/100,000) than with vaginal delivery, 7,000 of 89,775,000 (8/100,000) (relative risk 2.80, 95% CI 2.70-2.90) (p < 0.0001). The incidence was also higher in women aged 30-39 years, 6,000 of 35,039,000 (17/100,000) than in women aged 15-29 years, 6,000 of 77,673,000 (8/100,000) (relative risk 2.22, 95% CI 2.14-2.30) (p < 0.0001).

CONCLUSIONS: The incidence of amniotic fluid embolism has decreased since the early 1990s. The risk is higher with cesarean section and higher in women aged > or =30 years.