THE IMPACT OF PHYSICAL ACTIVITY AND STRESS ON FROZEN EMBRYO TRANSFER CYCLES: THE STEP AND STRESS TRACKING TO ESTIMATE PREGNANCY (SSTEP) TRIAL.

OBJECTIVE To investigate the impact of objectively measured physical activity and stress on programmed hormone replacement therapy (HRT) frozen embryo transfer (FET) outcomes. DESIGN Observational cohort study SUBJECTS: Patients undergoing standard HRT FET at a single academic center. EXPOSURE Average daily step counts before and after FET as measured by FitBit Charge 5 wearable activity tracker. MAIN OUTCOME MEASURES This longitudinal study involved 82 women undergoing a programmed HRT FET. Each participant wore a FitBit Charge 5 health tracker for the duration of their FET cycle. Variables tracked included daily average steps, activity zone minutes, daily calories burned, heart rate, and sleep duration. Participants were also asked to complete the Fertility Problem Inventory (FPI) at the start of their cycle to measure infertility-related perceived stress. Lastly, 6 salivary cortisol samples were obtained at three time points two days before embryo transfer. We then divided patients into 2 groups by those who conceived a pregnancy from the FET (n=51) versus those who did not (N=31) and compared FitBit variables and cortisol levels using Students t-tests and Poisson regression analysis. RESULTS On average, approximately 40 days of continuous health data was collected from subjects. When comparing those who conceived a pregnancy versus those who did not, there were no differences in average daily steps for the full study period, nor pre- or post- embryo transfer. Activity zone minutes, daily heart rate, daily calories burned, and sleep duration did not differ between the two groups pre- and post- embryo transfer. There was no difference in awakening cortisol, 30-minute post awaking cortisol, bedtime cortisol, or average cortisol awakening response between the two groups. Perceived stress measured by the FPI was largely the same when comparing the 2 groups. CONCLUSIONS In one of the first studies using wearable health trackers to examine in vitro fertilization outcomes, physical activity and stress did not influence the pregnancy rate in programmed HRT FET cycles.