Changes in Maternal Heart Rate and Autonomic Regulation following the Antenatal Administration of Corticosteroids: A Secondary Analysis

Antenatal corticosteroids, such as betamethasone, are standard clinical tools used to promote fetal maturation in cases of anticipated preterm birth. While their impact on fetal physiology is well documented, there has been surprisingly little research on how these synthetic hormones influence the mother's cardiovascular system. This study aimed to quantify the effects of betamethasone on maternal heart rate (HR) and heart rate variability (HRV), providing insights into how this common medication alters maternal autonomic regulation.

Researchers conducted a secondary analysis of data from 46 pregnant women with singleton pregnancies who were at risk of preterm delivery. Using abdominal ECG recordings, the team tracked maternal heart rate and HRV parameters—including time-domain, frequency-domain, and non-linear complexity features—for five days following the initiation of a standard betamethasone treatment regimen. The data were analyzed to detect changes in autonomic function and to identify when these changes returned to baseline levels.

The study revealed that betamethasone administration induces significant, transient changes in maternal physiology. Within 24 hours of the first dose, maternal HR increased by approximately 10 beats per minute, while HRV features associated with parasympathetic activity and heart rate complexity were significantly reduced. These changes indicate a temporary decrease in vagal control of the heart. By the third or fourth day post-administration, most cardiovascular metrics returned to pre-treatment levels, suggesting the acute effects are relatively short-lived.

These results are clinically important for obstetric monitoring. Because betamethasone can mimic or mask symptoms of tachycardia, clinicians should account for recent medication history when evaluating maternal vital signs. Furthermore, as HRV is increasingly used as a screening tool to assess maternal health and monitor for pregnancy complications, it is essential to distinguish between natural autonomic fluctuations and medication-induced physiological responses. The authors recommend that clinicians time maternal cardiovascular assessments either before or at least four days after the administration of betamethasone.