Exposure to 1918 Spanish flu in the womb had long-lasting effects

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Pregnant women, here’s another reason to consider getting vaccinated against the pandemic H1N1 influenza virus: Historical data show that men who were exposed to flu in the womb during the 1918 Spanish flu pandemic were 23% more likely than the general population to develop heart disease after the age of 60 and were slightly shorter then men born in the years preceding and following the pandemic, USC researchers reported today. And women exposed in the womb during the first trimester were 17% more likely to develop heart disease after age 60, according to the report in the Journal of Developmental Origins of Health and Disease. Those estimates are likely to be conservative, noted senior author Dr. Caleb Finch, a USC gerontologist, because those who were more severely affected are likely to have died before the age of 60.

Granted, the Spanish flu virus was much more lethal than the so-called swine flu virus has so far proved to be -- it killed 2% of the American population. But the data involve mothers who survived their infections and thus were likely to have suffered milder cases of disease. Moreover, pregnant women who contract the current swine flu virus are six times as likely as the general population to be hospitalized for complications, and those complications could impair the fetus’ further development.

Finch and his colleagues used data on 101,068 people born between 1915 and 1923 who responded to the National Health Interview Surveys conducted from 1983 to 1996 by the National Center for Health Statistics. From them, they calculated the increase in heart disease for those exposed to the virus in the womb. They also looked at Army enrollment health records for 2.7 million men whose year of birth ranged from 1915 to 1923. They found that the height of enrollees increased slightly every year during the period -- except for those who were born immediately after the pandemic. Their mean height was a statistically significant 0.05 inches shorter than that of those born in the preceding year.

Previous studies by the USC group have shown that inflammation and infections during pregnancy can impair the development of the fetus, both during the pregnancy and later in life. The new results appear to confirm those findings for influenza and give new urgency to efforts to vaccinate pregnant women.

-- Thomas H. Maugh II