What fetal parameter is most consistently affected by betamethasone (corticosteroid) administration?

From the Guidelines

Fetal heart rate variability is the fetal parameter most consistently affected by betamethasone administration. When betamethasone is given to pregnant women to accelerate fetal lung maturity (typically two 12mg doses given 24 hours apart), a transient decrease in fetal heart rate variability commonly occurs. This reduction typically begins within 24 hours of the first dose, is most pronounced after the second dose, and usually resolves within 72 hours after the last dose. This effect occurs because betamethasone crosses the placenta and temporarily alters fetal central nervous system activity, which controls heart rate variability 1. Healthcare providers monitoring fetal heart tracings should be aware of this normal, expected finding to avoid unnecessary interventions based on decreased variability alone. Other fetal parameters like baseline heart rate, accelerations, and decelerations are generally not affected in the same consistent manner. Understanding this effect is important for proper interpretation of fetal monitoring during and after betamethasone administration.

The use of antenatal corticosteroids, such as betamethasone, 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. The Society for Maternal-Fetal Medicine recommends offering a single course of antenatal corticosteroids to patients who meet the inclusion criteria of the Antenatal Late Preterm Steroids trial, and suggests consideration for the use of antenatal corticosteroids in select populations not included in the original trial 1. However, the long-term risks associated with antenatal corticosteroid use remain uncertain.

Key points to consider:

• Betamethasone administration can cause a transient decrease in fetal heart rate variability
• This effect is temporary and usually resolves within 72 hours after the last dose
• Healthcare providers should be aware of this normal, expected finding to avoid unnecessary interventions
• 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.

From the FDA Drug Label

Neonatal hypoglycemia has been reported after antenatal administration, especially in preterm, low birth weight infants, and when betamethasone is administered close to the time of delivery

The fetal parameter most consistently affected by betamethasone administration is blood glucose levels, as evidenced by the risk of neonatal hypoglycemia. This suggests that betamethasone may affect fetal glucose metabolism, leading to potential hypoglycemia after birth, especially in preterm or low birth weight infants 2, 2.

From the Research

Fetal Parameters Affected by Betamethasone Administration

The administration of betamethasone, a corticosteroid, has been studied for its effects on various fetal parameters. The key parameters affected include:

• Fetal lung maturation: Betamethasone has been shown to promote fetal lung maturation, which is crucial for reducing the risk of respiratory distress syndrome in preterm infants 3, 4.
• Umbilical artery blood flow: Studies have observed changes in the umbilical artery blood flow, including a decrease in the resistance index and pulsatility index after betamethasone administration 5, 6.
• Middle cerebral artery blood flow: An increase in the middle cerebral artery pulsatility index has been noted after betamethasone administration 6.
• Pulmonary artery blood flow: Betamethasone administration has been associated with changes in pulmonary artery blood flow, including an increase in acceleration time and acceleration time/ejection time ratio 6.

Short-Term Effects of Betamethasone

The short-term effects of betamethasone on fetal behavior and hemodynamics have been reviewed, highlighting both beneficial and undesirable effects 7. These effects include changes in fetal circulation and behavior, which can be used as markers of fetal well-being.

Relationship with Neonatal Respiratory Distress Syndrome

Research has explored the correlation between betamethasone administration and the development of neonatal respiratory distress syndrome (RDS) 6. The findings suggest that betamethasone administration can lead to changes in fetal pulmonary artery blood flow, which may be associated with a reduced risk of RDS. However, the relationship between these changes and the development of RDS requires further investigation.