Health Information

< Aug. 03, 2011 > -- Pregnant women exposed to high levels of electromagnetic fields - from power lines or electrical appliances - are more likely to have a child who later develops asthma.

That's the conclusion from a new study - the latest in a string of studies to examine the possible health effects of electromagnetic radiation - that appears in this week's Archives of Pediatrics and Adolescent Medicine.

Researchers in California asked 626 women to wear a monitor for 24 hours at some point in their pregnancy. The monitor measured the average daily exposure to electromagnetic fields (EMFs) produced by appliances and devices that ranged from electric blankets to fluorescent lights and included power lines.

Greater exposure, greater risk

The researchers then followed for up to 13 years the children born to those women. During that time, nearly 21 percent of the youngsters developed asthma. Children whose mothers had the highest magnetic field exposure (greater than 2 milligaus) were 3.5 times more likely to have asthma than the kids of women with the lowest exposure (0.3 milligaus or less).

The children of mothers who were in the middle group for magnetic field exposure were 74 percent more likely to have asthma than youngsters of moms in the lowest group.

About 10 percent of U.S. children have asthma, the CDC says. The number of children with asthma has been on the upswing recently, and researchers are trying to figure out why.

Amount of exposure

The study found that every 1 milligauss increase in average daily exposure was associated with a 15 percent increased risk of having asthma. Typically, exposure to EMFs comes in bursts, such as when using a microwave. But at other times, such as during sleep, people are not likely exposed to EMFs (unless they are using an electric blanket).

"This is a carefully executed and analyzed study with a very provocative finding," says Jonathan Samet, M.D., at the University of Southern California. "The association is strong and merits follow-up."

The study also found strong associations between EMFs and asthma in women whose children had other risk factors for developing asthma, including the mother having asthma herself or being the first-born child.

The children of mothers who had asthma and were exposed to high levels of EMFs had six times the chances of having asthma, and first-born children had a 40 percent increased risk of having asthma if their mothers were exposed to high levels of EMFs.

Widespread exposure

EMFs can be found just about everywhere in modern life, because anything powered by electricity or that generates electricity produces this type of radiation. Cell phones and other mobile communications devices also produce EMFs, but the study didn't measure this type of exposure because the EMF frequency of a mobile device is much different from that of an electric appliance.

Why EMFs might be harmful is unknown, although some studies suggest that EMFs may affect the fetus' developing immune system, possibly by disrupting communications between cells.

Lead author De-Kun Li, M.D., at Kaiser Permanente in Oakland, Calif., suggested that people stand at a distance from appliances when they're in use to minimize EMF exposure. For instance, a microwave emits 300 to 500 milligauss, but standing four to five feet away reduces exposure to about 1 to 2 milligauss, he says.

For a Healthy Pregnancy

If you're pregnant, following these guidelines can help keep you and your developing child healthy in the months ahead:

• Visit your health care provider regularly throughout your pregnancy.
• Don't take any medications without your doctor's OK. Both prescriptions and over-the-counter medications can cause birth defects.
• Don't smoke. Mothers who smoke have an increased risk of delivering prematurely and having a child with significant health problems.
• Don't drink alcohol. It can cause birth defects associated with fetal alcohol syndrome.
• Don't take illegal drugs. Doing so can cause birth defects and developmental delays in your child.
• Avoid exposure to toxic substances and chemicals, such as cleaning solvents, lead, mercury, some insecticides, paint thinners and paint removers.
• Eat a nutritious and balanced diet. You'll need extra protein, calcium, iron, and zinc. If you were at your ideal weight before you became pregnant, you will need about 300 additional calories a day from nutritious foods.
• Take 400 mcg of folic acid daily. Folic acid is a B vitamin that helps protect your unborn child from brain and spinal-cord birth defects.
• Stay physically active unless your doctor suggests otherwise. Exercise can help you feel better, reduce discomfort and fatigue, and promote a faster recovery after delivery.

Always talk with your health care provider to find out more information.