Do corticosteroids enhance fetal lung development?

From the Guidelines

Yes, corticosteroids do enhance fetal lung development. The use of antenatal corticosteroids has been widely adopted as the standard of care in the management of pregnancies at risk for preterm delivery before 37 weeks of gestation, with the primary goal of reducing neonatal morbidity 1.

Key Points

• Antenatal corticosteroids are recommended for pregnant women at risk of preterm delivery between 24 and 34 weeks gestation.
• The standard regimen is betamethasone 12 mg intramuscularly given twice, 24 hours apart, or dexamethasone 6 mg intramuscularly given four times, 12 hours apart.
• These medications cross the placenta and stimulate the production of surfactant, a substance that prevents the collapse of air sacs in the lungs.
• Corticosteroids also enhance structural maturation of fetal lungs by increasing the number of type II pneumocytes, thinning alveolar walls, and reducing lung fluid.
• The full effect begins approximately 24 hours after the first dose and lasts about 7 days.
• A rescue or repeat course may be considered if the initial treatment was more than 7 days prior and the pregnancy remains at risk for preterm delivery before 34 weeks.
• This treatment significantly reduces the risk of respiratory distress syndrome, intraventricular hemorrhage, and neonatal mortality in premature infants.

Recommendations

• We recommend offering a single course of antenatal corticosteroids to patients who meet the inclusion criteria of the ALPS trial, ie, those with a singleton pregnancy between 34 0/7 and 36 6/7 weeks of gestation who are at high risk of preterm birth within the next 7 days and before 37 weeks of gestation (GRADE 1A) 1.
• We suggest consideration for the use of antenatal corticosteroids in select populations not included in the original ALPS trial, such as patients with multiple gestations reduced to a singleton gestation on or after 14 0/7 weeks of gestation, patients with fetal anomalies, or those who are expected to deliver in <12 hours (GRADE 2C) 1.
• We recommend against the use of antenatal corticosteroids for fetal lung maturity in pregnant patients with a low likelihood of delivery before 37 weeks of gestation (GRADE 1B) 1.
• We recommend against the use of late preterm corticosteroids in pregnant patients with pregestational diabetes mellitus, given the risk of worsening neonatal hypoglycemia (GRADE 1C) 1.

From the Research

Effects of Corticosteroids on Fetal Lung Development

• Corticosteroids, specifically antenatal corticosteroids, have been shown to enhance fetal lung development and reduce the risk of respiratory distress syndrome (RDS) in preterm infants 2, 3, 4, 5.
• The use of antenatal corticosteroids, such as betamethasone, has been associated with improved lung compliance and surfactant concentration in the fetal lung 2.
• Studies have demonstrated that antenatal corticosteroid therapy can reduce the incidence of RDS, neonatal mortality, and other complications associated with preterm birth 3, 4, 5.

Mechanism of Action

• The exact mechanism of action of corticosteroids on fetal lung development is not fully understood, but it is thought to involve the regulation of gene expression and the promotion of surfactant production 2, 5.
• Corticosteroids may also have anti-inflammatory effects, which can help to reduce the risk of complications associated with preterm birth 3, 4.

Clinical Implications

• The use of antenatal corticosteroids is a standard practice in obstetrics for women at risk of preterm birth 3, 5.
• The optimal dosing and timing of antenatal corticosteroid administration are still being studied, but current evidence suggests that a single course of corticosteroids can be effective in reducing the risk of RDS and other complications 5.
• Further research is needed to determine the optimal use of antenatal corticosteroids in different populations, including women with multiple pregnancies and those in low-resource settings 5, 6.