The uterus is a dynamic muscular organ that undergoes rhythmic, wave-like contractions known as endometrial peristalsis or endometrial waves. This muscular activity, which is an essential component of natural fertility, presents a nuanced and sometimes contradictory role in the context of assisted reproductive treatments. Endometrial peristalsis refers to the frequency, amplitude, and pattern of myometrial contractions occurring in different reproductive phases. These peristalsis play vital roles in sperm transport, embryo migration, and implantation. Clinical and imaging studies suggest that abnormal patterns or excessive contractility at the time of embryo transfer may disrupt endometrial-embryo synchrony, impair implantation, and increase miscarriage risk. However, most evidence on endometrial peristalsis pertains to fresh embryo transfer cycles, natural conceptions, or pathological contexts, such as adenomyosis or fibroids, with limited insights regarding its effects on different endometrial preparation protocols in frozen embryo transfer (FET). Understanding the dynamics of endometrial peristalsis in this context is clinically important, as inappropriate contractile activity could physically expel the embryo or create a non-receptive environment, ultimately reducing the chances of live birth. Despite its theoretical significance, there is a paucity of robust, prospective data correlating endometrial peristalsis patterns measured around the time of FET with different endometrial preparation protocols with subsequent pregnancy outcomes.
Women aged 18 - 42 years old
Scheduled for frozen embryo transfer cycles using hormone replacement therapy protocol or natural cycle protocol (True natural cycles or modified natural cycles)
Transferred no more than two cleavage embryos or one good-quality blastocyst or no more than two poor-quality blastocysts
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 frozen embryo transfer during the study period.
Cohort
Prospective
Endometrial peristalsis and hormone measurements
Other interventionTime point for measurement 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 hCG trigger, (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 hCG trigger * On the transfer day prior to the procedure.
The association between live birth and uterine contraction frequency measured at different time points.
* Live birth was defined as the complete expulsion or extraction from a woman of a product of fertilization, after 22 completed weeks of gestational age; which, after such separation, breathes or shows any other evidence of life, such as heartbeat, umbilical cord pulsation, or definite movement of voluntary muscles, irrespective of whether the umbilical cord has been cut or the placenta is attached. A birth weight of 500 grams or more can be used if gestational age is unknown. Live births refer to the individual newborn; for example, a twin delivery represents two live births. * Uterine contraction frequency is defined as the number of peristaltic waves per minute.
The frequency of endometrial peristalsis at different time points
The frequency of endometrial peristalsis at different time points
Live birth rates after the one embryo transfer.
Live birth was defined as the complete expulsion or extraction from a woman of a product of fertilization, after 22 completed weeks of gestational age; which, after such separation, breathes or shows any other evidence of life, such as heartbeat, umbilical cord pulsation, or definite movement of voluntary muscles, irrespective of whether the umbilical cord has been cut or the placenta is attached. A birth weight of 500 grams or more can be used if gestational age is unknown. Live births refer to the individual newborn; for example, a twin delivery represents two live births.
Direction of peristalsis.
Direction of peristalsis is categorized as cervix-to-fundus, fundus-to-cervix, indeterminate, or absent (no contractions observed)
The correlation between endometrial peristalsis at different time points
The correlation between endometrial peristalsis at different time points.
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Mỹ Đức Hospital
Lead sponsor
My Duc Phu Nhuan Hospital HCMC, Vietnam
Collaborator
