Birth Weight Linked to High Blood Pressure Risk

NEW YORK (Reuters Health) - Men born at below-average weight are slightly more likely to have high blood pressure as young adults, a relationship that does not appear to be related to genetics or socioeconomic factors, the results of a large study from Sweden shows.

The findings support the theory that poor growth in the womb may cause disorders of the metabolism, such as high blood pressure (hypertension) or diabetes, known as the "fetal programming hypothesis," Dr. Niklas Bergvall of the Karolinska Institutet in Stockholm and colleagues report in the September issue of Epidemiology.

While past research has linked low birth weight to high blood pressure, most studies have not taken socioeconomic and genetic factors into account. Since both are tied to the risk of low birth weight as well as high blood pressure in adulthood, the relationship could be due to these factors, Bergvall and his team note.

To look at the effect of low birth weight independently, the researchers studied a group of Swedish men conscripted for military service, nearly 90,000 of whom had at least one brother available for comparison. Because brothers share half of their genes, on average, grow up in the same environment and have the same socioeconomic status, this allowed the researchers to control for the effect of these factors on the relationship between low birth weight and high blood pressure.

The researchers defined low birth weight as below 2,806 grams (6 pounds, 3 ounces) for babies born at 40 weeks gestation, and high systolic blood pressure as 140 mm/Hg or greater. Systolic pressure is the top number in a blood pressure reading.

After adjusting for these other factors, the researchers found that men born at low birth weight had a 14-percent greater risk of high systolic blood pressure in young adulthood.

"Our results lend some support to the fetal programming hypothesis, which states that metabolic disorders originate through adaptations in the malnourished fetus," they conclude.

SOURCE: Epidemiology, September 2005.