Dexamethasone and fetal heart rate variation

Area of Science:

• Obstetrics and Gynecology
• Fetal Medicine
• Pharmacology

Background:

• Antenatal corticosteroids like dexamethasone are used to accelerate fetal lung maturation.
• The impact of dexamethasone on fetal well-being, specifically fetal heart rate (FHR) patterns, requires thorough investigation.

Purpose of the Study:

• To investigate the effects of maternal dexamethasone administration on fetal heart rate and its variability.
• To compare the FHR response to dexamethasone in uncomplicated pregnancies versus those with fetal distress or growth concerns.

Main Methods:

• Retrospective analysis of computerized cardiotocograph data from 28 high-risk pregnancies (27-32 weeks gestation).
• Dexamethasone administered intramuscularly (12 mg twice, 12 hours apart) on 51 occasions.
• Fetal heart rate variables and umbilical artery flow velocity waveforms were analyzed before and after dexamethasone administration.

Main Results:

• A significant transient increase in short-term FHR variation was observed post-dexamethasone in pregnancies without fetal distress (P < 0.01).
• In pregnancies with fetal distress and high umbilical resistance, the increase in FHR variation was less pronounced (P < 0.01).
• Discordant twins showed differential responses, with one twin exhibiting sustained improvement while the other showed reduced response over time.

Conclusions:

• Maternal dexamethasone administration generally enhances fetal heart rate variation for approximately 24 hours.
• This beneficial effect is attenuated in conditions like pre-eclampsia or intrauterine growth retardation, potentially due to altered fetal steroid concentrations.
• The findings contrast with betamethasone, which has been associated with reduced FHR variation.