Preterm lung function after retreatment with antenatal betamethasone in preterm lambs

Area of Science:

• Neonatal Physiology
• Pulmonary Medicine
• Pharmacology

Background:

• Preterm birth is a leading cause of neonatal mortality.
• Antenatal corticosteroids, like betamethasone, are used to accelerate fetal lung maturation.
• The optimal dosing regimen for antenatal betamethasone is still under investigation.

Purpose of the Study:

• To investigate if a two-dose regimen of antenatal betamethasone, administered one week apart, enhances postnatal pulmonary function in preterm lambs compared to a single dose.
• To evaluate the impact of antenatal betamethasone retreatment on lung function and surfactant production in fetal sheep.

Main Methods:

• Fetal sheep at 121 days' gestation received either saline or a single dose of betamethasone (0.5 mg/kg).
• Six days later, fetuses were retreated with saline or betamethasone.
• Postnatal lung function was assessed one day after the second treatment.

Main Results:

• Betamethasone significantly improved lung compliance and ventilation efficiency by approximately 50%, and doubled total lung volume.
• No significant differences in pulmonary function were observed based on the treatment-to-delivery interval (1 vs. 7 days) or corticosteroid retreatment.
• While surfactant pool sizes increased with exposure duration, retreatment did not yield additional benefits.
• Antenatal betamethasone increased mRNA levels for surfactant proteins A and C; retreatment affected SP-B mRNA levels but suppressed SP-A and SP-C mRNA.

Conclusions:

• Antenatal betamethasone administration improves postnatal lung function in preterm lambs.
• Retreatment with betamethasone one week later did not further augment these improvements in pulmonary function or surfactant parameters.