Influenza (flu) is a highly contagious respiratory viral infection that circulates each year in the winter months and can cause serious illness in previously healthy people.
Unlike a cold, flu symptoms develop abruptly one to three days after infection, and can include: tiredness, high fever, chills, headache, sore throat, coughing, sneezing, runny noses, poor appetite, and muscle aches. Most people who get the flu will suffer from mild illness and recover in around four weeks. In some cases, severe illness and complications such as pneumonia can develop, which can result in hospitalisation and even death.
The immune system is one of the most important systems protecting the mother against the environment and preventing damage to her unborn baby. Immune responses are thought to be weakened in pregnancy to keep the body from rejecting the fetus, hence making pregnant women more susceptible to coughs, colds and flu. However, immune cells at the implantation site (placenta) are not suppressed, rather are active and carefully controlled, protecting the fetus from infection. It is now understood influenza in pregnancy is a hyperinflammatory disease rather than a state of immunodeficiency (Kay et al, 2014).
When pregnant women contract influenza, they tend to get very unwell due to the unique modulated immune response to ‘over-react to the flu’. Complications such as pneumonia are more common, with reports pregnant women are 5 times more likely to be admitted to ICU than other women who contract influenza. Additionally, influenza causes a 4 times greater likelihood of premature birth, again thought to be a result of interference with the maternal inflammatory pathway that is normally activated later in pregnancy to prepare the body for birth.
Influenza is therefore especially dangerous to pregnant women; annual vaccination is the best way of preventing the flu and any associated illness. The risk-benefit of vaccination during all stages of pregnancy has been carefully evaluated. The flu vaccine is redefined each year as protection is limited to those strains of virus from which the vaccine is prepared or closely related strains.
The 2017 seasonal influenza vaccine FluQuadri, is recommended and funded for pregnant women under the National Immunisation Program and safe to be given at any time during pregnancy. The flu shot provides effective protection (70-90% effectiveness overall) for you and your newborn baby for the first six months of their life, and is available from your GP or immunization provider.
For further information, see list below:
- Australian Government Immunise Australia website:
- National Centre for Immunisation Research and Surveillance fact sheets:
Mor, G & Cardenas, I. (2010). The Immune System in Pregnancy: A unique Complexity. American Journal of Reproductive Immunology, 63(6), 425-433. doi: 10.1111/j.1600-0897.2010.00836.x
Kay, A.W., Fukuyama, J., Aziz, N., Dekker, C.L., Mackey, S., Swan, G.E., Davis, M.M., Holmes, S. & Blish, C.A. (2014). Enhanced natural killer-cell and T-cell responses to influenza A virus during pregnancy. PNAS, 111(40), 14506-14511. doi:10.1073/pnas.1416569111