Antenatal Corticosteroids
A 23-year-old primigravida at 30 weeks is admitted with regular contractions and a cervix 2 cm dilated. Membranes are intact and the cardiotocograph is normal. She is given two doses of intramuscular betamethasone 12 mg, 12 hours apart, and asks what the injections are for. Which of the following neonatal complications is most reduced by this treatment?
- A.Neonatal hypoglycemia
- B.Respiratory distress syndromeCorrect
- C.Facial nerve palsy
- D.Spontaneous pneumothorax
Explanation
Antenatal corticosteroids act on fetal type II pneumocytes to accelerate surfactant synthesis and structural lung maturation, and they also promote maturation of the gut, brain and cardiovascular system. The principal benefit is a substantial reduction in neonatal respiratory distress syndrome, the disease of surfactant deficiency that causes grunting, retractions and a ground-glass appearance with air bronchograms on chest radiograph in preterm neonates. Randomized evidence also shows reductions in intraventricular hemorrhage, necrotizing enterocolitis, need for respiratory support and neonatal mortality. A course is either betamethasone 12 mg intramuscularly in two doses 24 hours apart, or dexamethasone 6 mg in four doses 12 hours apart, and the greatest benefit follows a completed course given between 24 hours and 7 days before delivery. Steroids are recommended when preterm birth is anticipated between 24 and 34 weeks, with selected use at 22 to 23 weeks and in the late preterm period. Neonatal hypoglycemia may in fact be slightly more common after late preterm steroids rather than less. Facial nerve palsy is a birth trauma from forceps, and pneumothorax is a complication of ventilation or of surfactant deficiency itself, not a target of steroids.
Why each option
- A.
- Antenatal steroids do not prevent neonatal hypoglycemia, and late preterm administration slightly increases it.
- B.
- Correct. Corticosteroids accelerate fetal surfactant production and markedly reduce respiratory distress syndrome, along with intraventricular hemorrhage and neonatal death.
- C.
- Facial nerve palsy results from birth trauma, usually forceps compression, and is unaffected by antenatal steroids.
- D.
- Pneumothorax is a complication of positive pressure ventilation or severe surfactant deficiency, not a primary endpoint of antenatal steroid therapy.
Reference: ACOG Committee Opinion No. 713, Antenatal Corticosteroid Therapy for Fetal Maturation, 2017 (reaffirmed 2023)
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