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Use of Surfactant Therapy Widens Gap in Death Rate of Black and White Newborns
St. Louis, June 18, 1996 -- Premature infants with undeveloped lungs have a better chance of surviving today due to the advent of surfactant therapy, a liquid that allows babies' lungs to inflate. After the Food and Drug Administration in 1990 approved the use of surfactant to treat potentially fatal breathing problems, the death rate of premature infants dropped significantly.
But a new study of 1,563 premature births in St. Louis by researchers at Washington University School of Medicine shows that the overall drop is due exclusively to a reduced number of deaths in premature white infants. After the introduction of surfactant therapy, the researchers found that the overall mortality rate of premature infants in the study dropped 16 percent. However, the drop was traced to a 41 percent decrease in the death rate of premature white infants. The researchers found no change in the death rate of premature black infants.
"We found that this therapy, which has been shown to be effective, did not have the anticipated effect on the disparity in the black and white newborn death rates once it became widely used in clinical practice," said Aaron Hamvas, M.D., lead author of the study and assistant professor of pediatrics.
Surfactant therapy is given to premature infants with respiratory distress syndrome (RDS). The breathing disorder strikes up to 50,000 of the 250,000 premature infants born annually in the United States and kills 5,000 each year. RDS is caused by the inability of the premature infants' lungs to make surfactant, which is produced in the lungs of a fetus starting in the last trimester and continuing until birth. Premature infants, those who weigh less than 4 pounds, generally do not produce enough surfactant to breathe on their own.
In the study, the researchers found the differences in death rates could not be explained by black babies' lack of access to surfactant, though premature white infants in the study were significantly more likely to receive surfactant therapy than their black counterparts. That's because the lungs of black fetuses mature more quickly than those of whites and, therefore, the incidence of RDS is lower in premature black infants. Moreover, the death rate of black and white babies who received surfactant was not significantly different - 20 percent of white infants and 23 percent of black infants who received the therapy died.
"On the surface, it looked like black babies didn't get as much surfactant, and therefore didn't have a reduction in mortality," Hamvas said. "But, actually, we found the differences in surfactant administration and the changes in the death rate were purely due to the differences in the incidence and severity of RDS. The babies who were sick enough to need surfactant got it, and it saved the same number of black and white babies."
The mortality rate for all infants is about 2.5 times higher for blacks than for whites. After the introduction of surfactant, the researchers found that black premature infants were three times more likely to die than white premature babies.
Hamvas compared birth and death certificates for all 1,563 very low birth-weight infants born in St. Louis with clinical data from the four St. Louis-area neonatal intensive care units during 1987-89 and 1991-92, before and after approval of surfactant for clinical use. Very low birth-weight infants are those weighing less than 3 pounds, 5 ounces.
The study found the neonatal death rate for very low birth-weight infants of all races decreased between the two intervals, from 220 deaths to 182 deaths per 1,000 births. The researchers credited the drop in the white death rate to a major decrease in deaths from RDS.
Although the incidence of RDS for whites remained stable during the two time periods, the study found the mortality rate for these newborns dropped 66 percent. In black very low birth-weight infants, the incidence of RDS rose slightly from 60 to 65 percent during the two time periods. However, Hamvas said the death rate for these newborns fell by only 11 percent.
Hamvas said the study shows there are a variety of other reasons premature infants die. "Because of this effective therapy, we have reduced one cause of death. But we're now unmasking other types of problems very low birth-weight infants might have," said Hamvas.
These problems, he said, may be attributed to a combination of biological, social and environmental factors such as infection, adolescent pregnancy or access to prenatal care.
Overall, the researchers said trying to prevent premature births is the most effective way to save babies. Hamvas suggested that understanding the causes of pre-term labor, preventing teenage pregnancy, and improving access to prenatal care and education programs may help reduce premature births and deaths related to prematurity.
"We've made great strides with our technology and treatment, but these advances may not result in greater social equity," Hamvas said. "The emphasis should be on preventing these babies from getting here early."