Endometrial peristalsis may influence embryo implantation and pregnancy outcomes, but its role during hormone replacement therapy (HRT)-prepared frozen embryo transfer (FET) cycles remains unclear. This prospective observational study will assess endometrial peristalsis at predefined time points during HRT-prepared FET cycles using transvaginal ultrasonography and evaluate its association with pregnancy outcomes. The study aims to clarify the clinical significance of endometrial peristalsis in HRT-prepared FET cycles and to provide evidence supporting endometrial assessment in assisted reproductive technology.
Women aged 18 - 42 years old
Scheduled for frozen embryo transfer cycles using hormone replacement therapy protocol
Transferred no more than two cleavage embryos or one good-quality blastocyst or no more than two poor-quality blastocysts
Provision of written informed consent to participate
Having an allergy and contraindications for exogenous hormone administration (e.g., breast cancer, thromboembolic disease)
Cycles with preimplantation genetic testing, oocyte donation, or in vitro maturation
Having untreated uterine or adnexal abnormalities (e.g., intrauterine adhesions, unicornuate/ bicornuate/ arcuate uterus, endometrial polyp, large leiomyoma ≥5 cm in diameter, hydrosalpinx, endometrial hyperplasia)
Use of uterine relaxants or intralipid infusion during the embryo transfer process
Women undergoing hormone replacement therapy frozen embryo transfer during the study period
Cohort
Prospective
Endometrial peristalsis and hormone measurements
Other interventionTime point for measurement of endometrial peristalsis will be assessed at three specific time points: * 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 Hormone measurements: serum levels of estradiol (E2) and progesterone (P4) will be assessed three times, on the same days as the endometrial peristalsis measurements, using electrochemiluminescence immunoassays. (Elecsys® Estradiol III and Elecsys® Progesterone III, Cobas® e 411, Roche Diagnostics, Germany): * On the second day to the fourth day of the menstrual cycle in the FET cycles * The day of progesterone initiation * On the transfer day prior to the procedure.
The correlation between endometrial peristalsis at different time points and live birth rates
The correlation between endometrial peristalsis at different time points and live birth rates
The frequency of endometrial peristalsis at different time points
The frequency of endometrial peristalsis at different time points
The correlation between endometrial peristalsis at different time points
The correlation between endometrial peristalsis at different time points
Direction of peristalsis
Direction of peristalsis is categorized as cervix-to-fundus, fundus-to-cervix, indeterminate, or absent (no contractions observed)
The association between endometrial peristalsis at different time points and pregnancy rates
The association between endometrial peristalsis at different time points and pregnancy rates
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