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Severe allergic reactions during pregnancy in the USA

Published online: May 15, 2019

Life threatening allergic reactions that cause breathing and circulatory problems are called anaphylactic reactions. These severe allergic reactions occur very rarely during pregnancy (UK rate: 1.6 per 100,000 pregnant women). A study in the UK showed that most of these reactions are caused by antibiotics or anesthetic drugs given to mothers around the time of a cesarean section. However, there is little information about how commonly these occur in the USA and whether anaphylaxis is related to cesarean section or other factors.

The study by McCall et al., recently published in The Journal of Allergy and Clinical Immunology: In Practice, used routinely collected data from a national sample of hospitalizations in the USA from 2004-2014. Diagnosis and procedure codes, which are recorded during every hospitalization, were used to identify pregnancy hospitalizations and those women who had an anaphylactic reaction.

The authors completed a number of analyses. First, they calculated how rare this severe reaction was in all pregnancies and in women who had a cesarean section. Second, they determined if this rate changed over the period 2004-2014. Third, they examined whether certain characteristics such as cesarean birth, race or history of an allergy were more common in women who had an anaphylactic reaction compared to those who did not.

The incidence of anaphylaxis in pregnancy was 3.8 per 100,000 pregnancy hospitalizations, and this was twice as high in those who had a cesarean section at 7.7 per 100,000 pregnancy hospitalizations. There was no major change in this rate over the period 2004-2014. Women who had an anaphylactic reaction, compared to those who did not, were more likely to have a cesarean delivery, to be of black or other (non-white) race and to have a history of a previous allergic reaction.

The incidence of anaphylaxis in pregnancy in the USA was twice as high as the UK; nevertheless, anaphylaxis remains a very rare complication of pregnancy in the USA. Although we do not know whether the cesarean birth was a cause or consequence of the reaction, the drugs given during a cesarean delivery may be an explanation for the higher rate amongst women having a cesarean birth. It is important that epinephrine is available during any surgical procedure occurring in the delivery suite or theater; epinephrine must be given immediately if anaphylaxis is suspected. Furthermore, a thorough medical history must be taken before any drugs are administered at childbirth; in particular, there should be an enhanced awareness of women who did not attend antenatal care to avoid administering an allergen to which they may be allergic.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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