In addition, the researchers examined height at World War II enrollment for 2.7 million men born between 1915 and 1922 and found that average height increased every successive year except for the period coinciding with fetal exposure to the flu pandemic.

Men who were exposed to the H1N1 flu in the womb were slightly shorter on average than those born just a year later or a year before, according to the study. The researchers controlled for known season-of-birth effects and maternal malnutrition.

"Prenatal exposure to even uncomplicated maternal influenza can have lasting consequences later in life," said Crimmins, professor of gerontology and sociology at USC. "The lingering influences from the 1918-1919 influenza pandemic extend the hypothesized roles of inflammation and infections in cardiovascular disease from our prior Science and PNAS articles to prenatal infection by influenza."

Indeed, the researchers note that they may have underestimated the effect of flu exposure on later life health. The study examined the relatively healthiest segment of Americans in 1918: the survivors of the pandemic. In addition, pandemic survivors who died of cardiovascular disease before the age of 60 were not sampled, presumably leaving out those who were the most susceptible to the effects of prenatal exposure.

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