Pregnant women can safely take flu shots without fear of harming their unborn child, informs the Norwegian Institute of Public Health. The institute has collaborated in an international study of the subject. (Illustrative photo: Albina Tiplyashina / Shutterstock / NTB scanpix)

Flu drugs safe for unborn babies

Pregnant women run a higher risk of getting seriously ill if they catch influenza. A new study shows that new-born infants run no higher risk of harm if their mothers have taken anti-viral medications to ward off flu infections.

Pregnant women should try to avoid coming down with the flu. The viral infection can in some cases cause serious complications for themselves and also premature births. This is why European and American health officials recommend that pregnant women take influenza vaccines as a precaution if they have come in close contact with someone who has the flu.

But what about their baby’s risk of a birth defect, ill health or morbidity in infancy? A number of studies down through the years have indicated an elevated risk of health problems for children if their mothers have taken specific medications during their pregnancies.

For instance a study has shown a higher risk of a child developing asthma if their mother used paracetamol while pregnant. 

So many women are sceptical about taking any medications during their pregnancies. A large study now shows at least that worries about complications caused by flu vaccines are unfounded. The antiviral drugs in question are known medically as neuraminidase inhibitors.

Researchers at the Norwegian Institute of Public Health (FHI) participated in the study, recently published in the journal BMJ.

Infections should be avoided

Senior Researcher Kari Furu at FHI thinks therefore that the results are important because many pregnant women run a chance of catching influenza during the annual peak season in winter.

“We already know that infections are to be avoided whenever possible during pregnancies. We don’t know enough about how infections affect the foetus. But earlier studies have shown that it can be unfortunate for the foetus if the mother catches the flu during her pregnancy,” she says.

This was shown in studies where researchers compared children of mothers who took shots against swine flu (H1N1 and H3N2v) with children whose mothers did not take this precaution.

This is why doctors recommend preventive medications to limit the infection to women who know they have been exposed to the flu.

Importantly, however, flu vaccines are not recommended during the first trimester of a pregnancy.

A cohort of 760,000 women

Senior Researcher Kari Furu at FHI and two colleagues have worked with researchers in Denmark, Sweden and France in comparing the new-born babies of 6,000 women who took drugs against influenza during their pregnancies with the infants of several hundred thousand women who did not take such anti-viral drugs.

“Over half of the exposed women were from Norway because the Norwegian authorities were more active in recommending the drugs to pregnant women,” explains Kari Furu.

They concluded that the medication-exposed infants had no more health problems that other new-borns.

The researchers say this is the largest study of its kind, as it covered the children of nearly 700,000 women in Norway, Denmark, Sweden and France.

Birth weights and congenital defects

When comparing the effects of flu vaccines, the medical researchers looked at birth weights, the Apgar score (which rates the new-born’s general condition at birth), incidences of pre-mature births, stillbirths as well as potential health issues such as congenital malformations.

Infants born to women who took the antiviral drugs – neuraminidase inhibitors – did not exhibit more health problems than other babies. There were no increases in premature births, stillbirths, or infant mortalities among the babies whose mothers had been medicated. Nor did these babies run a higher risk of congenital malformations or other health problems during their first four weeks of life.

The study thus confirmed previous ones which have pointed to the same conclusions.

“But these other studies have been too small for researchers to conclude with certainty that the medications were safe for the foetus,” explains Kari Furu.

The new study is based on the public health registers from several countries and is sufficiently large to reveal prospective differences between exposed and unexposed infants, according to the researchers.

The infants compared in the study were all new-borns in their first four weeks.

“We have not looked at possible long-term effects because there are so many other factors that can have an impact which we control,” says Furu.

Tamiflu against swine flu

Most of the women who had been prescribed a medication against influenza had taken Tamiflu, which can be taken preventively for five days after a person has been exposed to infection.

“Tamiflu can be used in treating influenza but also as a preventive drug if one has been exposed to an infection of flu virus. Another drug in the same category is Relenza, but it is very rarely used,” says Furu.

These drugs work by inhibiting the budding and reproduction of the flu virus within the body.

The women who were covered by the study gave birth during the period 2008 to 2010. Most of them took the medication in connection with the outbreak of swine flu.

The research about flu medications and pregnancies was financed by the Norwegian Institute of Public Health, the University of Bergen, Karolinska Institute in Sweden, Statens Serum Institut and the Medical Research Council in Denmark, the Hallas-Møller-stipend from Denmark’s Novo Nordisk Foundation and the Université Toulouse III in France.

Also on the subject of pregnancies and medications: Findings by the University of Oslo’s School of Pharmacy show that for many women with mental illnesses it is better for both the mother and her child if she uses medications for her illness rather than go through her pregnancy un-medicated. Multidisciplinary initiatives have been taken to provide better and balanced information to pregnant women about the use of such medications.


Read the Norwegian version of this article at

Translated by: Glenn Ostling

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