Health Library Antenatal Corticosteroids for Fetal Lung DevelopmentFrom Healthwise

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. Recent guidelines issued by the National Institutes of Health discourage such repeat courses of treatment, based on concerns about fetal harm from repeat treatments.¹

Corticosteroids are considered standard treatment for women who are 24 to 34 weeks pregnant and may deliver within the next 1 to 7 days, with or without preterm premature rupture of membranes (pPROM).¹

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 the occurrence of 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. However, considering the low-risk, high-benefit nature of this treatment, corticosteroids are typically used up to 34 weeks of pregnancy.

There is strong evidence that a single course of corticosteroid medication given to the mother during premature labor improves the outcome for the infant born between 24 and 34 weeks' gestation.²

Betamethasone or dexamethasone is most effective if delivery occurs at least 24 hours after the first dose of the medication has been given and less than 7 days after the last dose of the medication.

Either medication will benefit a premature newborn by decreasing the risk of:

• Breathing problems (respiratory distress syndrome) after birth.
• Bleeding in the brain (intraventricular hemorrhage).
• Intestinal infection (necrotizing enterocolitis).
• Death.

Corticosteroid side effects that might affect the mother can include fluid retention and increased blood pressure. However, they are short-term, 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 health professional 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.)

Fetal lung maturity testing (using amniotic fluid collected through amniocentesis) is occasionally used to determine whether antenatal corticosteroid treatment is necessary.

Repeat courses of corticosteroids given before birth are not recommended.¹ They may cause long-term effects on the growing child.³

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Citations

1. Antenatal Corticosteroids Revisited: Repeat Courses. NIH Consensus Statement, vol. 17, no. 2 (2000 August 17–18). Available online: http://consensus.nih.gov/2000/2000AntenatalCorticosteroidsRevisted112html.htm.

2. Banks BA, et al. (1999). Multiple courses of antenatal corticosteroids and outcome of premature neonates. American Journal of Obstetrics and Gynecology, 181(3): 709–717.

3. 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.

Author:	Kathe Gallagher, MSW	Last Updated: January 19, 2007
Medical Review:	Joy Melnikow, MD, MPH - Family Medicine Kathleen Romito, MD - Family Medicine William Gilbert, MD - Perinatology
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