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Prenatal Steroids Reduce Brain Injury in Preemies

Some of the tiniest premature babies are more likely to survive and have less brain injury if their mothers receive prenatal steroids. The finding provides the first strong evidence that steroids can benefit preemies born as early as the 23rd week of pregnancy.

Preterm babies are born before the 37th week of gestation, rather than the 40 weeks of a full-term pregnancy. Preterm birth occurs in over 10% of all pregnancies nationwide. It's a leading cause of infant death. Preemies also have increased risk for lung difficulties, developmental disorders and brain damage. Infants born before the 25th week of gestation are at particularly high risk for some degree of lifelong disability.

Medical guidelines currently recommend prenatal steroids for women at risk of giving birth between weeks 24 to 34 of pregnancy. The treatment improves fetal lung maturity, boosts infant survival and reduces the risk of brain injury. But the data on steroid therapy for births before the 25th week of gestation has been too limited to provide clear guidance for treatment.

To learn if steroid therapy might benefit these earliest preemies, researchers in the nationwide Neonatal Research Network analyzed medical records from more than 10,500 infants. All were delivered at 22-25 weeks' gestational age. The researchers also performed neurological exams on a subset of nearly 5,000 infants who survived 18 to 22 months after their original due dates. NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) supported the study.

The findings were reported on December 7, 2011, in the Journal of the American Medical Association. The scientists found that infants born to mothers who received prenatal steroids had 33% fewer deaths than those whose mothers didn’t. Among surviving infants, rates of blindness, hearing impairment, cerebral palsy or severe delays in motor and cognitive development were more than 20% lower when mothers had received prenatal steroids.

The researchers also looked at infant outcomes separately for each gestational week. For those born at weeks 23, 24 and 25, exposure to prenatal steroids was linked to significant reductions in death or neurological impairment by ages 18 to 22 months.

Prenatal exposure to corticosteroids also led to significantly fewer instances of other conditions among those born at 23-25 weeks. These included bleeding in the brain and a severe infection of the intestines known as necrotizing enterocolitis.

“We knew that many physicians were exercising their medical judgment to prescribe the treatment in cases not covered by the guidelines,” says study co-author Dr. Rosemary D. Higgins of NICHD. “These findings provide strong evidence that prenatal steroids can benefit infants born as early as the 23rd week of pregnancy.”