Endometrial Peristalsis and Pregnancy Outcomes in Hormone Replacement Therapy (HRT) - Frozen Embryo Transfer (FET) Cycles

Frozen embryo transfer (FET) has become an integral component of assisted reproductive technology (ART), and successful implantation depends on adequate endometrial receptivity. Different endometrial preparation protocols, including natural cycles and hormone replacement therapy (HRT) cycles, create distinct hormonal environments that may influence endometrial physiology. Among these protocols, HRT is the most widely used approach because it is applicable to a broad range of patients and offers greater flexibility in treatment scheduling.

Endometrial peristalsis, characterized by rhythmic contractions of the uterine junctional zone, is thought to play an important role in embryo transport and implantation. Previous studies have suggested that the frequency and direction of endometrial peristalsis are influenced by ovarian steroid hormones and may be associated with implantation and pregnancy outcomes. However, most available evidence has focused on natural menstrual cycles, while data regarding endometrial peristalsis during HRT-prepared FET cycles remain limited and inconsistent. The temporal changes in endometrial peristalsis throughout HRT endometrial preparation and their relationship with reproductive outcomes have not been fully elucidated.

This prospective observational study is designed to characterize endometrial peristalsis during HRT-prepared FET cycles using transvaginal ultrasonography and to evaluate the association between endometrial peristalsis and pregnancy outcomes. Endometrial peristalsis will be assessed at predefined time points during endometrial preparation, and pregnancy outcomes will be compared according to the observed peristaltic patterns. The results of this study are expected to improve understanding of endometrial physiology during HRT-prepared FET cycles and provide evidence on the clinical significance of endometrial peristalsis for reproductive outcomes.

• The frequency of endometrial peristalsis at different time points [Срок оценки: • On the second day to the fourth day of the menstrual cycle in the FET cycles. • The day of progesterone initiation (before progesterone exposure) • On the day of embryo transfer, immediately prior to the procedure]
• The correlation between endometrial peristalsis at different time points [Срок оценки: • On the second day to the fourth day of the menstrual cycle in the FET cycles. • The day of progesterone initiation (before progesterone exposure) • On the day of embryo transfer, immediately prior to the procedure]
• Direction of peristalsis [Срок оценки: • On the second day to the fourth day of the menstrual cycle in the FET cycles • The day of progesterone initiation (before progesterone exposure) • On the day of embryo transfer, immediately prior to the procedure]
• The association between endometrial peristalsis at different time points and pregnancy rates [Срок оценки: Up to delivery]
• Live birth rates after the one embryo transfer [Срок оценки: At delivery]
• Positive pregnancy test [Срок оценки: 10-14 days after embryo transfer]
• Clinical pregnancy [Срок оценки: 4-6 weeks after embryo transfer]
• Ongoing pregnancy [Срок оценки: 12 weeks of gestation or beyond]
• Implantation rate [Срок оценки: At 4-6 weeks after embryo transfer]
• Ectopic pregnancy [Срок оценки: Up to 12 weeks after embryo transfer]
• Miscarriage [Срок оценки: Up to 22 weeks of gestation]
• Multiple gestations [Срок оценки: At delivery]