Avian influenza during pregnancy linked to high mortality rates

Avian influenza during pregnancy linked to high mortality rates | Image Credit: © Jezper - © Jezper - stock.adobe.com.

Avian influenza virus infection during pregnancy is associated with high rates of maternal and infant mortality, according to a recent report from the Centers for Disease Control and Prevention.¹

The risks of severe disease and death from pandemics are increased among special risk populations. This includes pregnant women, who experienced increased mortality rates during the 2009 influenza pandemic and the COVID-19 pandemic. Therefore, public health efforts are necessary to protect this population before pandemic onset.

Cases of avian influenza A(H5N2) and A(H5N1) viruses in humans have been reported, leading to concerns about an increased pandemic risk. The first human case of H5N2, reported in a 59-year-old man from Mexico, led to mortality.

As seasonal influenza vaccination may impact H5N1 virus neutralizing antibody titers, understanding seroepidemiology may be challenging. However, while pregnant women may be at an increased risk of severe outcomes, this population is historically excluded from clinical trials of vaccines and therapies addressing pandemics.

Investigators conducted a systematic review to evaluate the impact of avian influenza virus infection in pregnant women. Articles were obtained through searches of the MEDLINE and EMBASE databases from inception until June 2024. Studies including pregnant women with avian influenza virus infections and reporting pregnancy outcomes were included.

Abstract and full text screening were performed by 2 independent reviewers. Controlled trial studies, cohort studies, observational studies, and case series or case reports were included in the analysis. Preterm birth was considered an outcome of interest, reported as live birth before 37 weeks’ gestation.

There were 8 studies included in the final analysis, 7 of which were individual case reports and 1 was a retrospective cohort study. These studies included 30 pregnant women presenting with avian influenza virus infection. Of these women, 16 were diagnosed with H5N1, 13 with H7N9, and 1 with H5N6.

These cases were often associated with exposure to poultry. Twelve women had attendance at live poultry markets or worked with live poultry, while 15 made contact with sick poultry. Patients were aged a median 20 to 35 years and at a gestational age of 8 to 36 weeks during infection.

Poor maternal and infant outcomes were reported in infected women, including a maternal death rate of 90% and an infant death rate of 86%. Only 5 infants survived, with 4 being born preterm. Of these births, 3 occurred during maternal infection through spontaneous labor or emergency cesarean section.

An infant birth at 35 weeks’ gestation was reported 2 months following maternal infection. Maternal and infant survival were not influenced by the timing of infection during pregnancy.

These results indicated poor maternal and infant outcomes from avian influenza virus infection during pregnancy. Reports about this information were limited, highlighting the need for increased awareness about how a new pandemic impacts pregnant women.

Risks may remain for offspring following birth, including increased odds of seizure. A study published in JAMA Network Open highlighted this heightened risk in infants born to mothers with influenza infection during pregnancy.²

The study reported an adjusted hazard ratio of 1.09 for seizures, 1.11 for febrile convulsions, and 1.04 for epilepsy among infants exposed to influenza when compared to those unexposed. This further supports the need for additional research about the impact of influenza infection on pregnancy outcomes.

References

1. Purcell R, Giles ML, Crawford NW, Buttery J. Systematic review of avian influenza virus infection and outcomes during pregnancy. Emerg Infect Dis. 2025. doi:10.3201/eid3101.241343
2. Krewson C. Maternal influenza linked to offspring seizure risk. Contemporary OB/GYN. September 23, 2024. Accessed December 18, 2024. https://www.contemporaryobgyn.net/view/maternal-influenza-linked-to-offspring-seizure-risk