Must Read: Pregnant Women Are Twice As Likely To Die From H1N1 Influenza Virus Infection

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A pregnant woman's immune system is suppressed to protect the fetus, which is recognized as a foreign body as it is genetically different. The study in mice, unfortunately, discovered that a dampened immunity during pregnancy gives the H1N1 influenza virus a chance to infect the mother.

According to Science Daily, the H1N1 influenza virus quickly mutates within a few days into a fatal strain. The findings of the latest study were published in Cell Host & Microbe on March 8.

"The first line of defense of the immune system, the innate immune response, is not acting quickly enough to clear the virus." Gülsah Gabriel, co-lead author and a virologist at the Heinrich Pette Institute, Leibniz Institute for Experimental Virology in Hamburg, Germany said.

As a result, the H1N1 influenza viruses have the opportunity to mutate rapidly, which is the best they can do. The newly produced variants now are responsible for an intensified virulence, he added.

After 100 years of many studies, scientists suggested that pregnant women suffer more seriously from influenza compared to their non-pregnant counterparts, Science Newsline reported. Pregnant women were seven times more probably to be hospitalized and twice as likely to die from H1N1 influenza virus infection than non-pregnant women. This was based on the 2010 World Health Organization review of the 2009 H1N1 influenza worldwide spread.

Based on previous studies, Gabriel also studied allogeneic pregnancies in mice in which the fetuses possess different genes from the mother. He was accompanied by Petra Clara Arck, co-lead author and a reproductive immunologist at the University Medical Center in Hamburg.

The two discovered that in allogeneic pregnancies, mother's immune system is more suppressed than in syngeneic pregnancies. Therefore, the H1N1 influenza viruses appear to take immediate advantage of the mother's susceptibility. Researchers found that a more suppressed mothers’ natural immunity is highly associated with an increased chance of the virus to survive and multiplies.

"In this environment of a dampened innate immune system, the virus has a chance to escape and become more virulent. This suggests that during pregnancy, a typical influenza infection could hit very hard," Gabriel said.

The World Health Organization prioritized pregnant women to get vaccinated targeting 75% of this population. This is in response to the 2009 H1N1 influenza virus pandemic.