Defining the Timing Window: Week- and Interval-Specific Effects of Antenatal Betamethasone in Late-Preterm Births

Area of Science:

• Obstetrics and Gynecology
• Neonatal Medicine
• Perinatal Research

Background:

• Late-preterm infants (34-36+6 weeks) face increased respiratory morbidity.
• Antenatal corticosteroids, like betamethasone, are used to mature fetal lungs.
• Optimal timing and impact of antenatal betamethasone in late-preterm births require further evaluation.

Purpose of the Study:

• To assess the association between antenatal betamethasone exposure and neonatal respiratory morbidity in late-preterm infants.
• To investigate if gestational age at delivery and exposure-to-delivery interval modify this association.
• To evaluate the risk of neonatal hypoglycemia following antenatal corticosteroid exposure.

Main Methods:

• Retrospective cohort study of singleton live births (34-36+6 weeks).
• Betamethasone exposure categorized as none, early (<34 weeks), or late (34-36+6 weeks).
• Exposure-to-delivery interval analyzed as ≤7 days or >7 days; outcomes assessed via logistic regression.

Main Results:

• Late antenatal corticosteroid exposure was linked to reduced odds of respiratory distress syndrome (RDS) and composite respiratory morbidity.
• However, late exposure also increased the odds of neonatal hypoglycemia.
• A significant reduction in RDS was observed at 34 weeks gestation with exposure ≤7 days, but not at later gestations or intervals >7 days.

Conclusions:

• Antenatal betamethasone exposure in late-preterm births has variable associations with neonatal respiratory outcomes.
• The benefits depend on gestational age at delivery and the timing of exposure relative to delivery.
• Findings suggest a potential respiratory benefit at 34 weeks within 7 days, balanced against metabolic risks like hypoglycemia.