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Last updated on April 24, 2014 at 17:35 EDT

Added Factors Can Increase Premature Infant Survival

April 17, 2008

New research showed that girls, babies that weighed more, babies who do not have a twin and babies whose mothers received steroids for lung development were more likely to survive being born prematurely.

Additionally, these factors were noted to minimize risk of problems including blindness, hearing loss and cerebral palsy.

“Using the five factors in combination really gives you a better idea of how children are going to do, rather than singling out a single factor,” said Dr. Rosemary Higgins of the National Institute of Child Health and Human Development (NICHD), who worked on the study.

Previously, the number of weeks spent inside of the womb was the primary factor that determined an infant’s survival rate.

The additional factors could count as much as an extra week of pregnancy, doctors said in the study, which was published in the New England Journal of Medicine.

“Sometimes gestational age can be off by a week or two, depending on dating or ultrasound,” said Higgins. “As you can see from the study, a week makes a big difference.”

Jon Tyson of the University of Texas Medical School at Houston, led a team of researchers that studied 4,446 infants born 22 to 25 weeks after conception. A full-term pregnancy lasts 40 weeks.

Overall, 49 percent of the infants in the study died, about 12 percent survived but had significant impairments, about the same number had even more severe physical or mental disabilities and 21 percent survived without a disability based on tests done when they were about two years old, researchers said.

“We found that about half of the infants survived and that about half of those who survived had neurodevelopmental impairments. This is a very, very high risk group of babies,” said Tyson.

Researchers reported that of babies that were born with a gestational age of 22 weeks, 95 percent died. Three-quarters of those born at 23 weeks died. After 24 weeks, less than half died. About three-quarters of infants who spent 25 weeks in the womb survived.

The researchers also found that in cases where boys and girls had equal chances of survival, girls were less likely than boys to receive intensive care. It’s not clear why, but Langer said heavier babies tend to get intensive care more often, and boys tend to be heavier.

The study was funded by the NICHD, which has turned the collected data into an online risk calculator to help doctors and families.

On the Net:

National Institute of Child Health and Human Development

NICHD Neonatal Research Network (NRN)

University of Texas Medical School