NEW YORK (Reuters Health) – Giving a single antenatal course of intramuscular corticosteroids after 34 weeks of gestation significantly enhances fetal lung maturity in pregnancies with documented fetal lung immaturity, research shows.

The use of antenatal steroids to enhance pulmonary function is recommended for pregnancies at risk of preterm birth at less than 34 weeks gestation, the study team notes in the May 17 online issue of the American Journal of Obstetrics and Gynecology. However, less is known about the effects of steroids among women at more advanced gestational ages.

While the incidence of respiratory distress syndrome is lower after 34 weeks, late-preterm infants are at higher risk of complications as compared with term infants and the ability of steroids to enhance fetal lung maturity during this period remains to be determined, the researchers note.

In their report, lead author Dr. Anthony Shanks from Washington University in St. Louis and colleagues describe 25 women between 34 and 36 weeks gestation with negative results on the TDx-FLM-II assay (Abbott) of fetal lung maturity markers. The TDx-FLM is an automated fluorescence polarization assay that measures mg surfactant/g of albumin in amniotic fluid and reports quantitative results.

Fifteen received no treatment and 10 received corticosteroids — either betamethasone 12 mg IM injection every 24 hours for 2 doses or dexamethasone 6 mg IM every 12 hours for 4 doses. This treatment is identical to that routinely given to women between 24 and 34 weeks