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BACKGROUND: Anaphylaxis in pregnancy is an understudied rare and severe complication of pregnancy. OBJECTIVE: To describe the incidence and temporal trends, and to identify potential risk factors for anaphylaxis related hospitalizations while pregnant in the USA METHODS: All hospitalizations while pregnant and any anaphylactic reactions were identified using ICD-9-CM codes from the National Inpatient Sample, USA over the period 2004-2014. Annual incidence rates of anaphylaxis during pregnancy were calculated. Logistic regression models assessed risk factors for anaphylaxis during pregnancy, presented as odds ratios and 95% confidence intervals. RESULTS: During the period 2004-2014, the incidence of anaphylaxis during pregnancy was 3.8 (95% CI: 3.4-4.2) per 100,000 hospitalizations while pregnant. The incidence did not statistically differ during the period 2004-2014. After adjustment, there were three factors that increased odds of anaphylaxis during pregnancy: caesarean delivery [aOR:4.19 (95% CI:3.28-5.35] compared to non-caesarean delivery; history of an allergic reaction [aOR: 4.05 (95%CI: 2.64-6.23)] compared to no history; a black race [aOR: 1.57 (95% CI: 1.15-2.15)] and other race [aOR: 1.69 (95%CI: 1.08-2.63) compared to white race. CONCLUSION: Despite increased rates of caesarean delivery in USA and consequent drug administration, there was no evidence of an increasing trend in anaphylaxis. Caesarean delivery and prior history of an allergic reaction allow the identification of women at risk of anaphylaxis. Not all women had clear risk factors and preparations should always be in place to ensure timely management if this uncommon event occurs.

Original publication




Journal article


J Allergy Clin Immunol Pract

Publication Date



Anaphylaxis, Caesarean section, Pregnancy, risk factors