Narrator: This is Science Today. Premature babies get a lot of transfusions, partly because they tend to be anemic -- they don't have enough red blood cells. Dr. Rod Phibbs of the University of California, San Francisco says that's not surprising. Babies in the womb have no problem making blood cells. Neither do full term babies.

Phibbs: But the system regulating that production of red blood cells turns off shortly after birth. And it looks as though it isn't programmed to turn back on until they get near the to time when they should have been born.

Narrator: Which is a month or more off for some premature babies. But doctors have found a way to jump start that system with a human hormone called erythropoieten, which stimulates red blood cell production. Phibbs led a nationwide study to see how well it worked in prematures.

Phibbs: We significantly reduced transfusions, and at the end of the treatment period the babies who received the treatment had significantly higher red blood cell counts, which meant there was going to be a lasting effect even after stopping the treatment.

Narrator: For Science Today, I'm Steve Tokar.