Current US guidance recommends the use of antenatal corticosteroids for mothers with preterm labor from 24 to 34 weeks' gestational age, but not before 24 weeks due to lack of supporting data. However, many infants born before 24 weeks' gestation are provided intensive care, therefore researchers investigated if use of antenatal corticosteroids is associated with improvement in major outcomes in this cohort.

Data were collected prospectively on infants (n = 10 541, birth weight 401-1000g) born at 22 to 25 weeks' gestation between January 1993, and December  2009, at 23 academic perinatal centers in the United States.

Certified examiners blind to exposure to antenatal corticosteroids performed follow-up examinations on 4924 (86.5%) of the infants born between 1993 and 2008 who survived to 18 to 22 months.

The main outcome measure, mortality and neurodevelopmental impairment at 18 to 22 months' corrected age was significantly lower for infants who had been exposed to antenatal corticosteroids and were born at 23 weeks' gestation (83.4% with exposure to antenatal corticosteroids vs 90.5% without exposure; adjusted odds ratio (AOR), 0.58 [95% CI, 0.42-0.80]), at 24 weeks' gestation (68.4% with exposure to antenatal corticosteroids vs 80.3% without exposure; AOR, 0.62 [95% CI, 0.49-0.78]), and at 25 weeks' gestation (52.7% with exposure to antenatal corticosteroids vs 67.9% without exposure; AOR, 0.61 [95% CI, 0.50-0.74]) but not in those infants born at 22 weeks' gestation (90.2% with exposure to antenatal corticosteroids vs 93.1% without exposure; AOR, 0.80 [95% CI, 0.29-2.21]).

If the mothers had received antenatal corticosteroids, the following events occurred significantly less in infants born at 23, 24, and 25 weeks' gestation: death by 18 to 22 months; hospital death; death, intraventricular haemorrhage, or periventricular leukomalacia; and death or necrotizing enterocolitis.

For infants born at 22 weeks' gestation, the only outcome that occurred significantly less was death or necrotizing enterocolitis (73.5% with exposure to antenatal corticosteroids vs 84.5% without exposure; AOR, 0.54 [95% CI, 0.30-0.97]).

In summary, antenatal corticosteroid therapy for mothers of infants born at 23, 24, and 25 weeks' gestation was associated with lower rates of both mortality and important morbidities, including a lower rate of death or severe neurodevelopmental impairment at 18 to 22 months' corrected age.