Changes in central hemodynamics and heart rate variability across active and placebo phases in second‐generation oral contraceptive pill users

Heart rate variability (HRV) is a popular, non‐invasive measure of cardiovagal tone. Some research has found that HRV increases from the follicular to the luteal phase of the menstrual cycle, however limited studies investigate the oral contraceptive pill (OCP) cycle. Therefore, the purpose of this study was to determine the influence of second‐generation OCP (OCP2) phase on HRV in the laboratory using electrocardiogram, and in a free‐living situation using the OURA® smart ring. 19 females using an OCP2 underwent measurements of HRV in the morning during the placebo and active phase of their OCP2 cycle and wore an OURA® smart ring. All HRV parameters, including those in the time and frequency domain, were lower in the active phase (all p 0.05) however, these differences did not persist after covarying for resting HR (all p > 0.05), except for ECG‐derived root mean square of successive differences and the standard deviation of successive differences. Diastolic and mean arterial blood pressure were lower in the active phase compared to the placebo phase ( p < 0.05). Therefore, we conclude that HRV is lower in the active phase compared to the placebo phase of the OCP2 cycle, reflecting the integrative regulation of cardiovascular homeostasis.