Pregnant mom's H1N1 swine flu exposure can harm baby

The sons of mothers who were pregnant and exposed to a strain of the H1N1 swine flu virus during the 1918 flu pandemic were more likely to have lifetime health problems, new research reveals, suggesting that even a mild case of the flu during pregnancy can have long-term affects on a baby.

The 1918-1919 flu pandemic infected one-third of Americans, killing about 0.6 percent of the population, notes the University of Southern California study, published Thursday in the Journal of Developmental Origins of Health and Disease .

The flu tended to be mild, causing a three-day fever. Most deaths were caused by secondary bacterial infections. But the flu's health effects, researchers now know, were far-reaching.

Using results from National Health Interview Surveys from 1982 to 1996, researchers found that men born in the first few months of 1919 -- those exposed to the flu during the second or third trimester -- were 23.1 percent more likely to have heart disease after the age of 60 than the overall population.

And World War II Army enlistment data for 2.7 million men born between 1915 and 1922 shows that the average height increased every successive year -- except for the period coinciding with fetal exposure to the flu. Men born in 1919 were shorter by about .05 inches.

Women, meanwhile, appear to have been less affected. Still, those born in the second quarter of 1919 -- who would have been exposed to the flu during the first

trimester -- were 17 percent more likely to have heart disease later in life than the general population.

"Prevention is the best medicine here and there's two aspects of that: One is not to get the flu, and if you do get the flu, take care of yourself so you don't get a secondary infection like pneumonia," said Caleb Finch, a USC professor of gerontology and biological sciences and the senior author of the study.

Finch said he decided to examine long-term health impacts of the 1918 pandemic after two Chicago economists, using U.S. Census data, found people exposed to the flu in utero that year were less successful.

They had lifetime deficits in economic productivity and education, which suggested they were developmentally impaired or struggled with health issues, the study said.

Studies looking at subsequent flu pandemics have revealed similarly disturbing health trends: Schizophrenia risk, for example, was three times higher in babies exposed to the flu in utero between 1959 and 1966.

Researchers theorize a mother's stress responses to an infection are key in causing abnormal fetal development, Finch said. Certain blood hormone and protein levels are elevated, which can accelerate chronic diseases of aging.

Maternal infection also can cause cortisol levels to spike, which in turn can affect a baby's adult vascular health, the study said. A type of interleukin -- a protein that mediates communication between cells -- can also surge, leading to increased adult blood pressure. In animals, it has been linked to abnormal brain development.

Understanding the long-term affects of prenatal exposure to the flu is important, since pregnant women are more likely to get the flu -- and die from it, according to a Centers for Disease Control and Prevention study published in August.

Six deaths of pregnant women with H1N1 were reported to the CDC between April 15 and June 16 this year, representing 13 percent of the total 45 deaths reported to CDC during that period. The women developed primary viral pneumonia.

One widely held belief is that younger people -- which includes pregnant women -- can have an overly-robust immune response to particularly virulent infections like H1N1, said D. Ware Branch, a perinatologist who practices at Intermountain Medical Center, and LDS and University hospitals. These "cytokinetic storms" are self destructive, attacking the healthy tissues in the body.

"In biology, there is a sweet spot: You don't want too much, you don't want too little," Branch said.

Gina Muscolino, an obstetrician-gynecologist at Lakeview Hospital in Bountiful, said she talks to her patients about the immediate problems associated with the flu, including cardiopulminary complications and hospitalization.

If a pregnant woman still refuses a flu shot, she said, she would consider bringing up potential long-term health effects on the unborn baby. But she doesn't expect to get that far with many patients.

"I've had women ask for the flu shot pretty regularly, and if I ask them if they want the flu shot, they take it," she said.

 

While the seasonal flu shot is readily available, it's still unclear to many providers when and how the H1N1 shot will be distributed once it arrives. Most local health departments have indicated they will keep the shots and do vaccinations themselves, which frustrates doctors like Muscolino, who see pregnant women daily.

"They [pregnant women] are at the highest risk -- they and small kids -- so I think we should be the first offices to get them," she said.

lrosetta@sltrib.com