Women who take antiviral drugs during their pregnancy pose no harm to their babies, new research shows.

A study conducted on more than 700,000 women found that developing children aren't adversely affected by common medications used to treat cold and flu.

The news will no doubt be a relief for millions of mothers-to-be, who are often prone to infections due to a weakened immune system. 

Scientists analysed the effects of oseltamivir (Tamiflu) and zanamivir on 6,000 pregnant women in Denmark, Norway, Sweden and France between 2008 and 2010.

They off-set the results against 700,000 pregnant women who weren't prescribed the drugs.

The team found no increased risks of adverse outcomes including low birth weight, low Apgar score (a test of a baby's condition at birth), preterm birth, stillbirth, or birth defects.

The findings remained the same when the analyses were restricted to oseltamivir exposure only.

Published in the British Medical Journal, the study's authors claim its the largest of its kind to assess potential risks of taking antiviral drugs (known as neuraminidase inhibitors) during pregnancy.

They add that their results 'support previously reported findings that the use of neuraminidase inhibitors is not associated with increased risks of adverse fetal or neonatal outcomes.'

The data comes one year after Australian researchers claimed expectant mothers who have the winter flu jab slash their chance of having a stillbirth by more than half.

The study, led by the University of Western Australia, found that women who had been recently vaccinated against flu were 51 per cent less likely to have a stillbirth than women who were unvaccinated.