High Blood Pressure May Start in the Womb
Excerpt By Amy Norton, Reuters Health

NEW YORK (Reuters Health) - New research supports the theory that some cases of high blood pressure may have roots that go back to fetal development.

What's more, researchers say, their findings suggest that proper nutrition during pregnancy could be a very early way to cut the risk of high blood pressure years later.

That's only speculation for now, but the new findings are in line with recent work suggesting that prenatal factors can have health effects that last into adulthood. There is evidence, for example, tying low birth weight to a higher risk of cardiovascular disease decades later.

This latest, small study now shows that people with primary hypertension--high blood pressure not caused by another disease--may have fewer nephrons in their kidneys than people with normal blood pressure do.

Nephrons are the tiny filtration units that do the kidneys' work of expelling waste and excess fluid from the body--a process that plays an important role in regulating blood pressure. The nephron number is set during fetal development, and a normal kidney is estimated to contain about 1 million nephrons, although that number varies among individuals.

The authors of the new study suspect that the lower nephron number they found in individuals with high blood pressure is the result of their having been born with a relatively lower number of nephrons.

The study cannot "definitely answer" this question, but past animal and human research has supported the concept that a low nephron number might leave a person more vulnerable to high blood pressure, Dr. Kerstin Amann told Reuters Health.

Amann, a professor at the University of Erlangen-Nurnberg in Germany, led the study. The findings are published in the January 9th issue of The New England Journal of Medicine (NEJM).

Amann's team based their conclusions on examinations of kidneys from 20 middle-aged, white people, mostly men, who had died in accidents. Ten had had high blood pressure.

Although much more research is needed, these early findings point to the potential importance of prenatal nutrition in determining a person's eventual vulnerability to high blood pressure, according to Amann.

There is evidence, for example, that low protein intake during pregnancy could affect nephron number in the fetus, as well as the risk of high blood pressure and other types of cardiovascular disease in adulthood.

"Improving nutrition for pregnant women could be one strategy in preventing low nephron number and perhaps also hypertension," said Amann.

An NEJM editor agrees that good prenatal nutrition is "one possible preventive action."

However, high blood pressure has multiple risk factors, Dr. Julie R. Ingelfinger adds in an accompanying commentary.

"It would be an oversimplification to state that nephron number alone is the key to primary hypertension," she writes.

In addition, Amann pointed out, it is unknown if the current findings apply to different racial and ethnic groups. This is important because certain groups, including African Americans, have particularly high rates of hypertension.

SOURCE: The New England Journal of Medicine 2003;348:101-108.

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