Is there any benefit to antenatal corticosteroids (ACS) within 12 hours of administration?

Benefits of Antenatal Corticosteroids Within 12 Hours of Administration

Yes, there are benefits from antenatal corticosteroids (ACS) that begin to appear within the first 12 hours after administration, though the maximum benefits occur between 24 hours and 7 days after the first dose. 1

Timing of Benefits

• Initial benefits (0-24 hours):

  • Benefits begin to appear within the first 24 hours after administration 1
  • Even a single dose administration can improve neurodevelopmental outcomes in cases of imminent preterm birth 2

• Maximum benefit period:

  • Optimal benefits occur between 24 hours and 7 days after administration 1
  • Most significant improvement in fetal lung maturation occurs between 24-48 hours after the first dose 1
  • Maximum reduction in respiratory morbidity (33% reduction) is achieved between 48 hours to 7 days 1

Clinical Application Based on Timing

• For imminent delivery (<12 hours):

  • The Society for Maternal-Fetal Medicine (SMFM) suggests consideration for ACS use in patients expected to deliver in <12 hours (GRADE 2C recommendation) 3
  • Even partial courses provide some benefit, so administration should not be withheld if delivery is expected within 12 hours

• For high-risk IUGR cases:

  • When absent or reversed umbilical artery end-diastolic flow is noted at <34 weeks, antenatal corticosteroids should be administered, with close observation for 48-72 hours following administration 3
  • Transient return of end-diastolic flow may occur in about two-thirds of cases after steroid administration 3

Dosing Considerations

• Standard regimen:

  • Betamethasone: 12 mg intramuscularly, two doses 24 hours apart 1
  • Complete course (both doses) provides maximum benefit 1

• Partial course:

  • Even incomplete courses provide some benefit
  • European guidelines note that even a single-dose administration should be given to women with imminent preterm birth 2

Important Caveats

• Patient selection:

  • Avoid ACS in patients with low likelihood of delivery before 37 weeks (GRADE 1B) 3
  • Use caution in patients with pregestational diabetes mellitus due to increased risk of neonatal hypoglycemia (GRADE 1C) 3

• Risk-benefit assessment:

  • Benefits are most established for pregnancies between 24 0/7 and 33 6/7 weeks 4, 5, 6
  • For late preterm (34 0/7 to 36 6/7 weeks), benefits are more modest and must be weighed against potential risks 7

• Long-term considerations:

  • Long-term risks of ACS remain uncertain, and patients should be counseled accordingly (GRADE 1C) 3
  • Continued surveillance of long-term outcomes after in utero corticosteroid exposure is recommended 5

In summary, while the maximum benefit of ACS occurs after 24 hours, there is evidence supporting administration even when delivery is expected within 12 hours, as some benefit begins to appear early and even partial courses can improve neonatal outcomes.