Antenatal steroid injections are a common medical intervention used during pregnancy when there is a concern about premature birth. These injections help accelerate the baby’s development before birth.
Purpose of Antenatal Steroids
Antenatal steroids are given to pregnant women at risk of preterm birth, typically between 24 and 34 weeks of gestation, to accelerate fetal lung maturity. Preterm birth can lead to respiratory distress syndrome (RDS) in newborns, a condition where underdeveloped lungs struggle to function due to a lack of surfactant. Surfactant is a substance that helps keep the tiny air sacs in the lungs open.
The administration of corticosteroids like betamethasone or dexamethasone stimulates the production of surfactant phospholipids by the baby’s lung cells. This helps the lungs mature quickly, reducing RDS likelihood and severity. A single course of antenatal corticosteroids can reduce RDS occurrence by about 50%. It also lowers the risk of other serious complications in preterm infants, such as bleeding in the brain (intraventricular hemorrhage) and necrotizing enterocolitis, a severe intestinal condition.
The Ideal Timeframe for Delivery
Antenatal steroid injections are most effective when given within a specific timeframe before delivery. Benefits typically begin within 24 to 48 hours after the first dose, with peak effectiveness lasting up to 7 days after administration.
Medical guidelines recommend aiming for delivery within this 7-day window to maximize the steroid’s protective effects on the baby’s lungs. The most studied regimens involve either two doses of betamethasone 12 mg given intramuscularly 24 hours apart, or four doses of dexamethasone 6 mg given intramuscularly 12 hours apart. While some benefit may still be observed if delivery occurs outside this window, optimal reduction in respiratory complications is seen when birth happens within this peak period.
Outcomes Outside the Optimal Window
If a baby is born before the antenatal steroids have had sufficient time to take effect, typically less than 24 hours after the first dose, full benefits may not be realized. In such cases, the baby may still have a higher risk of respiratory complications, including more severe respiratory distress syndrome, compared to infants born within the optimal 24-hour to 7-day window. This is because the steroid needs time to stimulate lung development.
Conversely, if delivery occurs more than 7 days after the steroid injections, the primary benefits of the medication may have waned. While some residual effect might still exist, the strong protective benefits on lung maturity diminish over time. In these situations, medical professionals assess the baby’s condition and the ongoing risk of preterm birth to determine the best course of action, which may include additional interventions.