Emerging data reveal surprising patterns in maternal–fetal outcomes linked to avian influenza virus infection.
A recent Centers for Disease Control and Prevention (CDC) report suggests that avian influenza virus infection in pregnant individuals may lead to a high risk of both maternal and infant death.1 Historically, vulnerable populations—particularly pregnant women—have experienced increased disease severity and mortality during pandemics, as observed in both the 2009 influenza pandemic and the coronavirus disease 2019 (COVID-19) pandemic. Given these data, proactive public health measures for pregnant populations warrant special consideration prior to the pandemic's onset.
Multiple cases of avian influenza A(H5N2) and A(H5N1) viruses in humans have been recorded, including the first documented H5N2 infection in a 59-year-old man in Mexico, which resulted in death.2 This has raised concerns about the potential for an avian influenza pandemic. Interpreting seroepidemiologic data can be complex because prior vaccination with a seasonal influenza vaccine may alter H5N1-specific neutralizing antibodies, and pregnant individuals are frequently excluded from the vaccine and therapeutic clinical trials investigating novel pandemic agents.
The Centers for Disease Control and Prevention (CDC) is reporting that the patient identified with the first severe case of the avian influenza A(H5N1) in the US has differing mutations from previous cases and strongly suggests that the changes emerged during infection as virus replicated in the patient.1
Investigators undertook a systematic review to assess the impact of avian influenza virus infection in pregnancy. Searches of the MEDLINE and EMBASE databases from their inception up to June 2024 were performed to identify articles describing pregnant individuals infected with avian influenza virus, with pregnancy outcomes reported. Studies that met inclusion criteria comprised controlled trials, cohort studies, observational designs, and case series or case reports. Two reviewers independently screened abstracts and full texts. Preterm birth, defined as delivery prior to 37 weeks’ gestation, was among the outcomes of interest.
Of the 8 studies that fulfilled inclusion criteria, 7 were individual case reports and 1 was a retrospective cohort investigation. Together, these publications described 30 pregnant patients with confirmed avian influenza virus infection: 16 with H5N1, 13 with H7N9, and 1 with H5N6. Poultry exposure was a frequent risk factor: 12 patients had contact with live poultry markets or direct handling of poultry, and 15 had sick-poultry exposure. The median age of infected patients ranged from 20 to 35 years, and infections occurred at gestational ages ranging from 8 to 36 weeks.
Maternal mortality was reported at 90%, and infant mortality was 86%. Among the 5 infants who survived, 4 were born preterm. In 3 instances, delivery was prompted by active infection and occurred via spontaneous labor or emergent cesarean section. One neonate was delivered at 35 weeks’ gestation approximately 2 months following maternal infection. The timing of infection during gestation did not substantially change maternal or neonatal survival rates.
These findings underscore the severe risks associated with avian influenza infection during pregnancy, although the evidence base remains limited. Furthermore, there is a need for heightened attention to how emerging pandemics may disproportionately affect pregnant populations.
Beyond the immediate gestational period, there may be ongoing adverse effects for offspring. A study published in JAMA Network Open reported an elevated risk of seizures in infants born to mothers with influenza infection during pregnancy.2 The investigators noted an adjusted hazard ratio of 1.09 for seizures, 1.11 for febrile convulsions, and 1.04 for epilepsy in exposed infants compared with unexposed controls. These data further highlight the importance of ongoing research into the long-term implications of maternal influenza infection for both maternal and child health.
