Black baby girls born weighing 2.2 pounds or less are more than twice as likely to survive as white baby boys born at the same weight, when many preemies are still too tiny to make it on their own, University of Florida researchers have found.
Analyzing data from more than 5,000 premature births, UF researchers pinpointed a link between gender and race and the survival rates of babies born at extremely low weights, according to findings released in the journal Pediatrics. It's the first scientific evidence of a phenomenon doctors have observed for years, said Steven B. Morse, M.D., M.P.H., a UF assistant professor of pediatrics and the article's lead author.
Baby girls of both races had the strongest advantage when born weighing less than 1,000 grams, about 2 pounds or as much as a quart of milk, Morse said. Girls had nearly twice the odds of surviving as baby boys did, and black infants also had a slight survival advantage over whites, the research shows. Overall, black baby girls were twice as likely to survive compared with white baby boys, 1.8 times more likely to survive than black boys and 1.3 times more likely to live than white baby girls.
"When you're talking about survival, that's very significant," Morse said. "We have known in general that females tend to have better survival rates than males and blacks better than whites. But quantifying that and finding if there was a statistical significance had yet to be done."
Morse and other researchers from the UF Maternal Child Health Education and Research and Data Center also analyzed the infants' developmental ages and weights at birth, combining these data with race and gender to specify the odds of survival for babies born in each demographic.
Nationwide, nearly a half million babies are born prematurely each year, according to the National Center for Health Statistics. Only about 1 percent of all babies born weigh less than 2 pounds, and one of the first questions parents of these infants ask is if their child will live, said Morse, who as a neonatologist works with families every day. Having accurate data can help families and doctors make better decisions at a time when choices can be hard to make, he said.
"I'm trying to get as much information as I can before the baby is born to give the parents a realistic expectation of survival," he said. "Not all babies are the same, especially with regard to survival at this early gestational age. There are differences based on race and gender, so we can't group all these babies together and say survival at less than 1,000 grams is X-percent."
UF researchers studied vital statistics from 5,076 babies born in Florida between 1996 and 2000 and weighing less than 1,000 grams. The influence of gender and race on babies' survival rates was more noticeable the smaller the infants were, the research shows. The higher the weights and developmental ages were at birth, the more survival rates increased for all babies.
About 1,500 babies included in the study were extremely premature, born when their mothers were less than 24 weeks pregnant. On average, these babies had a less than 27 percent chance of survival. Because their organs have not had as much time to develop, these tiny babies are at the highest risk for disabling health problems, and doctors and families often struggle to decide what life-saving measures should be taken, if any, Morse said.