Women who receive the influenza or whooping cough vaccine during a twin pregnancy do not face an increased risk of birth complications, according to new research from the University of Queensland. The study reveals that a significant majority, approximately 72 percent of women pregnant with twins, were unvaccinated against these illnesses, highlighting a critical gap in vaccine uptake.
The research, which examined 11,435 infants born from 5,757 twin pregnancies in Queensland and the Northern Territory over a six-year period from 2012 to 2017, indicates that the vaccines are safe and do not heighten the risks of preterm birth, stillbirth, or small-for-gestational-age infants.
Research Findings and Implications
Dr. Lisa McHugh, a researcher in the School of Public Health at UQ, emphasized the necessity of this study. Previous research focused primarily on singleton pregnancies, leaving a significant information gap regarding twin pregnancies, which inherently carry different risks. “Twin pregnancies cannot be compared to singleton pregnancies in studies, and this is why we felt it was important to address this research gap,” Dr. McHugh stated.
The study’s findings reveal that only 2 percent of women pregnant with twins received the influenza vaccine, while 16 percent received the whooping cough vaccine. In comparison, in the same time frame and regions, 14 percent of women with singleton pregnancies received the flu shot, and 30 percent were vaccinated against whooping cough.
“Our findings provide robust evidence that these vaccinations are safe and do not increase the risk of adverse birth outcomes,” Dr. McHugh added. Moreover, the study found a 15 percent lower risk of small babies among those vaccinated against whooping cough in Queensland, a 22 percent reduction in preterm births in Northern Territory pregnancies, and a 7 percent decrease in preterm births for those vaccinated against influenza in Queensland.
Addressing Vaccine Hesitancy
Lead author and UQ Master of Epidemiology graduate Kahlee Boyle noted the importance of this research in reassuring both medical professionals and expectant mothers. “Healthcare providers are crucial to influencing vaccine acceptance during pregnancy, and we want general practitioners to be able to inform patients about this local Australian study confirming the vaccines are safe,” she said.
These vaccines are fully funded for pregnant women under Australia’s National Immunisation Program, yet the uptake remains lower than desired. Vaccine confidence has notably declined in recent years, largely due to misinformation, particularly during the COVID-19 pandemic.
Dr. McHugh highlighted the vulnerability of infants to severe influenza and whooping cough due to their immature immune systems. “Babies born early or small may also have underdeveloped lungs, placing them at a much higher risk of a life-threatening illness if unvaccinated,” she explained. Given that twins often face a higher likelihood of being born prematurely or at a lower weight, this research underscores the critical need for vaccine safety studies focused on twin pregnancies.
Additionally, pregnant women experiencing respiratory illnesses like influenza are at an elevated risk of severe outcomes, including hospitalisation, intensive care, or death, especially in the third trimester.
The findings of this important study are published in BJOG: An International Journal of Obstetrics and Gynaecology, providing a significant contribution to the understanding of vaccine safety in twin pregnancies and helping to address ongoing concerns regarding maternal and infant health.
