Antenatal corticosteroids for fetal lung development
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How It Works
Betamethasone and dexamethasone cause an immature fetus's lungs to produce a compound called surfactant. A full-term baby's lungs naturally produce surfactant, which lubricates the lining of the air sacs within the lungs. This allows the inner surfaces of the air sacs to slide against one another without sticking during breathing. Premature infants whose lungs have begun producing surfactant have an improved ability to breathe on their own, or with less respiratory treatment, after birth.
When preterm birth between 24 and 34 weeks of pregnancy (gestation) is expected within 7 days, betamethasone or dexamethasone is given to the mother in order to affect the fetus. Betamethasone is given in 2 injections, 24 hours apart. Dexamethasone is given every 12 hours for 4 doses.
If delivery does not occur within 7 days of treatment, the injections should not be repeated.
Why It Is Used
Betamethasone and dexamethasone are corticosteroids, also called glucocorticoids, that are given before birth (antenatally) to speed up a preterm fetus's lung development. Either is used when a mother is in preterm labor and birth may occur in 24 to 48 hours. This helps prevent respiratory distress syndrome (RDS) and related complications following premature birth.
Many infants born at 33 to 34 weeks' gestation have sufficient lung maturity to breathe on their own. But considering the low-risk, high-benefit nature of this treatment, corticosteroids are typically used up to 34 weeks of pregnancy.
How Well It Works
There is strong evidence that a single course of corticosteroid medicine given to the mother during premature labor improves the outcome for the infant born between 24 and 34 weeks' gestation.1
Betamethasone or dexamethasone is most effective if delivery occurs at least 24 hours after the first dose of the medicine has been given and less than 7 days after the last dose of the medicine.
Either medicine will benefit a premature newborn by lowering the risk of:
Corticosteroid side effects that might affect the mother can include fluid retention and increased blood pressure. But these are short-term side effects and less likely to occur at all during such a short period of treatment. These side effects are more of a concern during long-term treatment for other health problems.
Control of diabetes may be more difficult in pregnant women when corticosteroids are used. Your doctor may recommend a different insulin dose during this time.
See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)
What To Think About
- Haas DM (2008). Preterm birth, search date June 2007. Online version of BMJ Clinical Evidence: www.clinicalevidence.com.
- American Academy of Pediatrics and American College of Obstetricians and Gynecologists (2007). Obstetric and medical complications. In Guidelines for Perinatal Care, 6th ed., pp. 175–204. Elk Grove Village, IL: American Academy of Pediatrics.
- French NP, et al. (2004). Repeated antenatal corticosteroids: Effects on cerebral palsy and childhood behavior. American Journal of Obstetrics and Gynecology, 190(3): 588–595.
Last Updated: January 14, 2009
Author: Sandy Jocoy, RN