Eleven RCTs were included in the review (n=4,390 women and 5,227 babies). Sample sizes of included trials ranged from 12 to 1,858 women. Study quality of the RCTs ranged from 6 to 8 out of 8.
Compared with a single course, multiple courses of antenatal corticosteroids were associated with a statistically significant decrease in respiratory distress syndrome (RR 0.80, 95% CI 0.71 to 0.89, I2=0%; six studies, n=2,785), patent ductus arteriosus (RR 0.74, 95% CI 0.57 to 0.95, I2=24%; five studies, n=4,031), ventilator support (RR 0.84, 95% CI 0.77 to 0.91, I2=47%; four studies, n=4,480), surfactant use (RR 0.75, 95% CI 0.67 to 0.84, I2=0%; six studies, n=5,032) and any maternal side-effects (RR 0.79, 95% CI 0.66 to 0.96, I2=94%; three studies, n=3,327).
Compared with a single course, multiple courses of antenatal corticosteroids were associated with a statistically significant decrease in birth weight (WMD -83, 95% CI -124.47 to -42.55, I2=0%; seven studies, n=5,372) and head circumference (WMD -0.35, 95% CI -0.52 to -0.17, I2=43%; seven studies, n=5,089).
There was no statistical difference between single course and multiple course antenatal corticosteroids for 15 other outcomes, which included composite neonatal mortality, perinatal death, endometritis and severe respiratory distress syndrome.