The incidence and outcomes of anaphylaxis in pregnancy: a UK population-based descriptive study.Objective: Anaphylaxis is a potentially fatal systemic hypersensitivity reaction, characterised by life -threatening airway, breathing or circulatory problems often with skin or mucosal change. Recent policy changes recommending administration of prophylactic antibiotics prior to caesarean delivery have led to concerns about the maternal and fetal impacts of anaphylactic reactions. The aim of this study was to estimate the incidence of anaphylaxis in pregnancy and describe the management and outcomes in the UK.
Methods:A population based descriptive study was completed using the UK Obstetric Surveillance System (UKOSS) between 1 st October 2012 and 30 th September 2015. Cases of anaphylaxis were defined as a severe, life-threatening generalised or systemic hypersensitivity reaction.
Results:There were 37 confirmed cases of anaphylaxis in pregnancy, giving an estimated incidence of 1.6 (95%CI 1.1-2.2) per 100,000 maternities. In cases with a single agent recorded, the main causal agents were as follows: penicillin based antibiotics (n=9), cephalosporins (n=1), imidazole (n=1), oxytocin (n=1), anaesthetic agents (n=3), blood products (n=3) and intravenous iron (n=2). There were four cases of anaphylaxis in women with known penicillin allergies: two had received co-amoxiclav and two cephalosporins. Twelve women had anaphylaxis following prophylactic use of antibiotics at the time of a caesarean delivery. Two women died (5%), 14 (38%) women were admitted to intensive care and seven women (19%) had one or more additional severe maternal morbidities, which included three haemorrhagic events, two cardiac arrests, one thrombotic event and one pneumonia. No infants died; however, in those infants whose mother had anaphylaxis before delivery (n=18) there were 7 (41%) neonatal intensive care unit admissions, 3 preterm births and one baby was cooled for neonatal encephalopathy.
Conclusions:Anaphylaxis is a rare severe complication of pregnancy and frequently the result of a reaction to antibiotic administration. This study highlights the seriousness of the outcomes of this condition for the mother. The low incidence is reassuring given the large proportion of the pregnant population that receive prophylactic antibiotics during delivery.