Experts found that the likelihood of developing the disease was considerably higher for people exposed to a H1N1 strain of influenza A while in the uterus.
Caleb Finch, senior author of the study, said, ‘Our point is that during pregnancy, even mild sickness from flu could affect development with longer consequences.’
The findings come from research carried out on more than 100,000 individuals born during and around the time of the 1918 influenza pandemic in the United States. The outbreak killed two per cent of the total population.
Finch admits that the 1918 flu was far more lethal than any since. ‘Nonetheless,’ he says, ‘there is particular concern for the current swine flu which seems to target pregnant women. Prospective mums should reduce risk of influenza by vaccination.’
He and his colleagues found that men born in the first few months of 1919 – who would have been in the second or third trimester during the height of the epidemic – had a 23.1 greater chance of having heart disease over the age of 60 than the rest of the population. For women, however, the results showed that those born in the second quarter of 1919 – who would have been in the first trimester during the epidemic’s height – were 17 per cent more likely to have heart disease later in life than their peers. This points to possible gender differences in the effects of flu exposure.
Additionally, the researchers found that men exposed to the H1N1 flu in the womb were slightly shorter on average than those born the year before or after the pandemic. The researchers controlled for known season-of-birth effects and maternal malnutrition.