BABIES born before their lungs have fully developed usually have breathing problems, sometimes serious ones. Might the chance of such problems be reduced if a pregnant woman who's likely to give birth prematurely is given periodic injections with a corticosteroid?

A study involved 982 pregnant women who were considered to have a good chance of delivering prematurely. All had received one corticosteroid injection. They then were randomly assigned to have weekly injections with the corticosteroid betamethazone or a saline solution (placebo) through their 32nd week of pregnancy. Fewer babies born to women who had the drug injections had respiratory illnesses (33% vs. 41%) or severe lung disease (12% vs. 20%). The babies in each group had about the same number of infections, and their average size when they left the hospital was nearly identical. There also was little difference between the groups in the average gestational age at birth and the proportion of babies born prematurely.

Who may be affected by these findings? Women at risk of delivering at 37 weeks of pregnancy or earlier. Although any woman can deliver prematurely, this occurs more often in women who have had a previous preterm birth, who are carrying multiple foetuses or who have certain uterine or cervical abnormalities.

Caveats: The study followed babies until initial discharge from the hospital; it did not determine any longer-term effects. Other studies have reported increased infections at birth and abnormal growth and development in childhood when mothers had been given prenatal corticosteroids repeatedly. An editorial published with this study advised that "routine use of multiple courses of antenatal corticosteroids should be considered with caution until results from long-term follow-up studies are known."

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