From the Guidelines
Fetal heart rate variability is the fetal surveillance parameter most consistently affected by betamethasone administration. When betamethasone is given to pregnant women to accelerate fetal lung maturity, a temporary reduction in fetal heart rate variability commonly occurs, as noted in the context of antenatal corticosteroid use 1. This effect typically begins within 24 hours of the first dose, is most pronounced 48-72 hours after initiation of therapy, and usually resolves within 4-7 days. The decreased variability results from betamethasone crossing the placenta and affecting the fetal central nervous system, temporarily altering autonomic nervous system regulation of the fetal heart. Key points to consider include:
- The administration of antenatal corticosteroids, such as betamethasone, has been widely adopted to reduce neonatal morbidity in preterm deliveries 1.
- The Society for Maternal-Fetal Medicine recommends offering a single course of antenatal corticosteroids to patients at high risk of preterm birth within the next 7 days and before 37 weeks of gestation 1.
- Healthcare providers monitoring fetal heart tracings should be aware of the expected pattern change in fetal heart rate variability to avoid unnecessary interventions.
- Other parameters like baseline heart rate, accelerations, and decelerations are less consistently affected by betamethasone administration. Given the current evidence, it is crucial for healthcare providers to be aware of the effects of betamethasone on fetal heart rate variability to ensure appropriate interpretation of fetal surveillance parameters and to minimize unnecessary interventions, thus prioritizing the well-being and safety of both the mother and the fetus 1.
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 surveillance parameter most consistently affected by betamethasone administration is neonatal blood glucose levels, as indicated by the potential for neonatal hypoglycemia.
- Key points:
- Neonatal hypoglycemia has been reported after antenatal administration of betamethasone.
- This effect is especially notable in preterm, low birth weight infants.
- The risk is increased when betamethasone is administered close to the time of delivery 2.
From the Research
Fetal Surveillance Parameters Affected by Betamethasone Administration
The administration of betamethasone, a corticosteroid, has been observed to affect several fetal surveillance parameters. Key findings from various studies include:
- Fetal breathing movements: Studies have consistently shown that betamethasone administration leads to a decrease in fetal breathing movements 3, 4, 5.
- Fetal body and limb movements: A reduction in fetal body and limb movements has been reported following betamethasone administration 4, 5.
- Nonstress test: The nonstress test, a component of the biophysical profile, has been shown to be affected by betamethasone administration, with an increase in non-reassuring fetal heart rate tracings 3, 5.
- Biophysical profile score: Betamethasone administration has been associated with a decrease in biophysical profile scores, primarily due to the reduction in fetal breathing and body movements 3, 4, 5.
Doppler Velocimetry Parameters
In contrast to the effects on biophysical profile parameters, Doppler velocimetry parameters have been found to be largely unaffected by betamethasone administration:
- Umbilical artery Doppler: No significant changes in umbilical artery Doppler indices have been reported following betamethasone administration 4, 5, 6.
- Middle cerebral artery Doppler: Similarly, middle cerebral artery Doppler indices have been found to be unaffected by betamethasone administration 4, 5, 6.
- Ductus venosus Doppler: One study reported a decrease in ductus venosus pulsatility index following betamethasone administration, but this finding is not consistent across all studies 7.