Comment on “The Impact of Physical Activity and Stress on Frozen Embryo Transfer Cycles: The Step and Stress Tracking to Estimate Pregnancy (SSTEP) Trial”

Optimizing outcomes in frozen embryo transfer (FET) cycles during in vitro fertilization (IVF) is an important aspect of fertility treatment, and patients frequently ask about lifestyle changes to improve chances of pregnancy. Current evidence surrounding activity restrictions at the time of embryo transfer has been conflicting, and some studies have shown that many patients self-restrict activity even when not instructed to by their clinic. Patients also frequently ask about the effect of emotional stress on IVF outcomes. This study was designed to address these 2 questions using a validated questionnaire for stress, cortisol levels, and physical activity as measured by step counts.

This was a prospective observational cohort study of patients undergoing standard programmed FET cycles between June 2022 and February 2024. Inclusion criteria were age <35 with a transfer of a single untested blastocyst embryo or age 35 or greater, transferring a single euploid blastocyst embryo. Exclusion criteria were abnormal uterine pathology, endometrial lining <6 mm after hormonal preparation, gestational carriers, and a history of recurrent miscarriage or recurrent implantation failure. The primary outcome for this study was the clinical pregnancy rate.

The final analysis included 82 patients. At baseline, those who achieved pregnancy were older and more likely to have used preimplantation genetic testing for aneuploidy (PGT-A). Other baseline characteristics were similar between groups. The average percentage of time wearing the FitBit device used for this study was 96.2%. There were no significant differences in average total daily step counts or in step counts before or after the embryo transfer between those who achieved pregnancy and those who did not. Patients who achieved pregnancy had an increase in daily step count after embryo transfer, while those who did not had a decrease in daily step count; though this trend was observed, step count was not a significant predictor of pregnancy. Other physical activity measurements were not significantly different between groups. Sensitivity analysis showed similar results.

In terms of stress, global stress index scores were not significantly different in patients who achieved pregnancy versus those who did not, and neither group had scores indicating high infertility-related stress. Cortisol levels were determined through saliva samples, and there were no significant differences in cortisol between patients who achieved pregnancy and those who did not. In addition, sexual activity was not significantly different between groups.

These results indicate that physical activity, stress, and sexual activity are likely not related to whether a patient will conceive after an FET cycle, but rather that other variables are responsible for driving pregnancy rates posttransfer. This is consistent with the most recent published literature showing that bed rest after embryo transfer does not improve pregnancy rates. Future studies should assess the potential relationship of decreased physical activity after transfer with lower pregnancy rates, as well as evaluate the influence of sexual activity on FET outcomes.

(Summarized from Jacobs E, Summers K, Van Voorhis B. The impact of physical activity and stress on frozen embryo transfer cycles: the Step and Stress Tracking to Estimate Pregnancy (SSTEP) Trial. Fertil Steril . 2026;125(3):401-410. doi:10.1016/j.fertnstert.2025.08.039).