Late preterm infants (born at 34 to 36 weeks) have a significantly reduced likelihood of respiratory complications if their mothers undergo prenatal steroid therapy, according to a new study from the National Institutes of Health (NIH) published in the New England Journal of Medicine.

“Reducing neonatal respiratory complications could result in less injury to the immature lung, less hospitalizations, earlier infant-mom bonding, and better long-term lung and general health,” said Carol Blaisdell, MD, medical officer at the National Heart, Lung, and Blood Institute.

Pregnant women who are likely to deliver before 34 weeks receive steroids as part of standard treatment to reduce their infants’ risk of complications (including respiratory ones) and death. Now, evidence supports steroid use in pregnant women likely to deliver before 37 weeks to reduce infants’ risk of respiratory complications.

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The study, conducted by Uma Reddy, MD, MPH, of the Pregnancy and Perinatology Research Branch at the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development, and colleagues, included 2,831 women in their 34th to 36th week of pregnancy who were at high risk of delivering before 37 weeks. Participants were randomly assigned to receive two injections 24 hours apart of either the steroid betamethasone or a placebo.

The primary outcome included the need for therapy to treat difficulty breathing (including continuous positive airway pressure [CPAP], oxygen therapy, and mechanical ventilation) and whether an infant was stillborn or died within 72 hours of birth.

In the betamethasone group, 11.6% of infants met the primary outcome criteria – the need for respiratory therapy was 20% less compared with the placebo group. Two infants in the betamethasone group died within 72 hours, but neither death was from respiratory causes.

The researchers also measured rates of severe respiratory illness, defined by the need for CPAP or supplemental oxygen for ≥12 continuous hours, a high concentration of oxygen for ≥24 hours, or mechanical ventilation. In the betamethasone group, 8.4% of infants had severe respiratory illness, 33% less than the placebo group. Infants in the betamethasone group were also less likely to have transient tachypnea and bronchopulmonary dysplasia.

Infants in the betamethasone group were more likely to have low blood sugar compared with the placebo group. The researchers recommend monitoring neonatal blood sugar levels if steroids are administered. No other differences in rates of complications were observed between the two groups.


  1. Gyamfi-Bannerman C, Thom EA, Blackwell SC, et al. Antenatal Betamethasone for Woman at Risk for Late Preterm Delivery. N Engl J Med. 2016; doi:10.1056/NEJMoa1516783.