As an adjunct to the recent post on baby gooroo® on the effect of antenatal corticosteroids on the timing of lactogenesis II, recent data suggest that multiple courses of antenatal corticosteroid therapy may also interfere with fetal growth. Moreover, it appears to offer no significant advantage.

The results of a study were presented January 30, 2008 by Canadian researcher, Kellie Murphy, MD, at the Society for Maternal-Fetal Medicine 28th Annual Meeting. It is the largest study so far to investigate how much is enough when it comes to antenatal corticosteroid use. A single antenatal course has been shown to protect high-risk fetuses from respiratory distress syndrome and neonatal death; the question was whether repeated courses offer even greater benefit. Based on the data, the answer appears to be no.

Murphy and colleagues examined 1858 pregnant women at high risk for preterm birth. Participants were given an initial course of corticosteroid therapy; 2 to 3 weeks later they were randomly assigned to receive either placebo (n = 1140) or corticosteroids (n = 1164) every 2 weeks until 33 6/7 weeks’ gestation or birth, whichever came first.

The incidence of infant mortality, severe respiratory distress syndrome, intraventricular hemorrhage, periventricular leukomalacia, bronchopulmonary dysplasia, and necrotizing enterocolitis were recorded.

Results showed that infants born to women who received multiple courses of corticosteroids experienced rates of morbidity and mortality similar to those born to women in the single-course group (12.9% vs 12.5%; odds ratio, 1.4; 95% confidence interval [CI], 0.77 – 1.39; P = .83).

However, the infants whose mothers received repeated courses of corticosteroids were born smaller and had a smaller head circumference. Their average weight was 2216 g compared with 2330 g for those infants whose mothers were in the single-course group (P = .00260), length was 44.5 cm vs 45.4 cm (P = .00075), and head circumference was 31.1 cm vs 31.7 cm (P = .0001).

“Multiple courses of antenatal corticosteroids, every 14 days, are not recommended,” Dr. Murphy said during her presentation. She and her colleagues are now following the infants in the study to see whether the differences in size have a later clinical significance.

At the present time, it appears that there is no benefit to the use of multiple courses of antenatal corticorsteroids,” said Dr. Murphy.

“Currently, a single course of corticosteroids is the recommended standard of care,” said Katharine Wenstrom, MD, president of the Society for Maternal-Fetal Medicine.

“Clearly,” she added, “the data call into question any future rationale for multiple courses.”