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NCT Number: NCT07358468

Impact Of FET Preparation Protocol On Endometrial Peristalsis: A Prospective Cohort Study

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.

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Key information

Age range

18 year–42 year

Sex eligibility

Female

Study type

Observational

Primary location

IVFMD Phu Nhuan - My Duc Phu Nhuan Hospital, Ho Chi Minh City, Vietnam

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About this study

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 uterine contractility pertains to fresh embryo transfer cycles, natural conceptions, or pathological contexts, such as adenomyosis or fibroids, with limited insights regarding its effects on different FET protocols. Several studies have demonstrated an inverse relationship between endometrial peristalsis and IVF success. Masroor et al. found that patients with lower endometrial peristaltic wave frequency (<4 waves/min) before embryo transfer had significantly higher chances of clinical pregnancy and live birth compared to those with more frequent peristalsis. Similarly, Chung et al. reported that increased endometrial peristalsis frequency immediately after embryo transfer was linked to reduced live birth rates, suggesting that excessive motility may physically expel the embryo or disturb its implantation. In the prospective cohort study of 292 infertile women, Zhu et al. found that lower uterine peristaltic wave frequency (<3.0 waves/min) before embryo transfer is associated with higher clinical pregnancy rates in both fresh and frozen-thawed embryo transfer cycles. In a study by Vuong et al. on patients with repeated implantation failure, they found that administering atosiban to patients with uterine peristalsis exceeding 16 waves per 4 minutes could improve pregnancy rates.

Different protocols for endometrial preparation in FET cycles, including natural cycles and hormone replacement therapy (HRT) cycles, create distinct hormonal environments that influence endometrial peristalsis and may impact pregnancy outcomes. Understanding how endometrial peristalsis varies by protocol and its effect on pregnancy outcomes is essential for optimizing IVF strategies.

Therefore, this study aims to evaluate endometrial peristalsis patterns in different FET protocols and their association with pregnancy outcomes.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • 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

Exclusion criteria

  • 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.
  • Use of a GnRH-agonist for downregulation within one month.
  • PCOS patients

Treatment and study plan

Endometrial peristalsis and hormone measurements

Other

Time 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 progesterone initiation or LH surge/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 progesterone initiation or LH surge/hCG trigger
  • On the transfer day prior to the procedure.

Primary outcomes

  1. The frequency of endometrial peristalsis at different time points, and different FET protocol.

    Time frame: • On the second day to the fourth day of the menstrual cycle in the FET cycles. • The day of progesterone initiation or LH surge/hCG trigger, (before progesterone exposure) • On the day of embryo transfer, immediately prior to the procedure

    Frequency is defined as the number of peristaltic waves per minute.

Secondary outcomes

  1. Direction of peristalsis.

    Time frame: • On the second day to the fourth day of the menstrual cycle in the FET cycles. • The day of progesterone initiation or LH surge/hCG trigger, (before progesterone exposure) • On the day of embryo transfer, immediately prior to the procedure

    Direction of peristalsis is categorized as cervix-to-fundus, fundus-to-cervix, indeterminate, or absent (no contractions observed)

  2. The association between endometrial peristalsis at different time points and pregnancy rates

    Time frame: Up to delivery

    The association between endometrial peristalsis at different time points and pregnancy rates

  3. The correlation between endometrial peristalsis at different time points

    Time frame: • On the second day to the fourth day of the menstrual cycle in the FET cycles. • The day of progesterone initiation or LH surge/hCG trigger, (before progesterone exposure) • On the day of embryo transfer, immediately prior to the procedure

    The correlation between endometrial peristalsis at different time points.

  4. Live birth rates after the one embryo transfer.

    Time frame: At delivery

    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.

  5. Positive pregnancy test

    Time frame: 10-14 days after embryo transfer

    Defined as serum human chorionic gonadotropin level ≥ 25 mIU/mL.

  6. Clinical pregnancy

    Time frame: 4-6 weeks after embryo transfer

    A pregnancy diagnosed by ultrasonographic visualization of one or more gestational sacs or definitive clinical signs of pregnancy. In addition to intra-uterine pregnancy, it includes a clinically documented ectopic pregnancy.

  7. Ongoing pregnancy

    Time frame: 12 weeks of gestation or beyond

    A pregnancy diagnosed by ultrasonographic or clinical documentation of at least one fetus with a discernible heartbeat at 12 weeks gestation or beyond.

  8. Implantation rate

    Time frame: At 4-6 weeks after embryo transfer

    The number of gestational sacs observed divided by the number of embryos transferred (usually expressed as a percentage).

  9. Ectopic pregnancy

    Time frame: Up to 12 weeks after embryo transfer

    A pregnancy outside the uterine cavity, diagnosed by ultrasound, surgical visualization, or histopathology.

  10. Miscarriage

    Time frame: Up to 22 weeks of gestation

    Spontaneous loss of a clinical pregnancy before 22 completed weeks of gestational age, in which the embryo(s) or fetus(es) is/are nonviable and is/are not spontaneously absorbed or expelled from the uterus.

  11. Multiple gestations

    Time frame: At delivery

    A pregnancy with more than one embryo or fetus.

  12. Multiple birth

    Time frame: At delivery

    The complete expulsion or extraction from a woman of more than one fetus, after 22 completed weeks of gestational age, irrespective of whether it is a live birth or stillbirth. Births refer to the individual newborn; for example, a twin delivery represents two births.

  13. Mode of delivery

    Time frame: At delivery

    Vaginal delivery, C-section (elective, suspected fetal distress, non-progressive labor).

  14. Birth weight

    Time frame: At delivery

    Weight of the newborn measured right after delivery.

  15. Gestational age at birth

    Time frame: At delivery

    Calculated by gestational age of all live births.

  16. Preterm birth

    Time frame: At delivery

    Defined as delivery at <28, <32, <37 completed weeks. A birth that takes place after 22 weeks and before 37 completed weeks of gestational age.

  17. Gestational diabetes mellitus

    Time frame: At 24-28 weeks of gestation

    A 75-g OGTT, with plasma glucose measurement when the patient is fasting and at 1 and 2 h, at 24-28 weeks of gestation in women not previously diagnosed with diabetes.

  18. Hypertensive disorders of pregnancy

    Time frame: Up to delivery

    Hypertensive disorders of pregnancy: Pregnancy-induced hypertension, pre-eclampsia (early and late), eclampsia, and HELLP syndrome are defined in the American College of Obstetricians and Gynecologists (ACOG) 2020 g

  19. Stillbirth

    Time frame: Up to delivery

    The death of a fetus before the complete expulsion or extraction from its mother after 28 completed weeks of gestational age. The death is determined by the fact that, after such separation, the fetus does not breathe or show any other evidence of life, such as heartbeat, umbilical cord pulsation, or definite movement of voluntary muscles. Note: It includes deaths occurring during labor.

  20. Very low birth weight

    Time frame: Up to delivery

    Birth weight less than 1.500 g.

  21. Low birth weight

    Time frame: Up to delivery

    Birth weight less than 2.500 g.

  22. High birth weight

    Time frame: Up to delivery

    Implies growth beyond an absolute birth weight, historically 4.000 g or 4.500 g, regardless of the gestational age.

  23. Very high birth weight

    Time frame: Up to delivery

    Birth weight over 4.500 g for women with diabetes, and a threshold of 5000 g for women without diabetes.

  24. Major congenital abnormalities

    Time frame: Up to delivery

    Structural, functional, and genetic anomalies that occur during pregnancy, and are identified antenatally, at birth, or later in life, and require surgical repair of a defect, or are visually evident, or life-threatening, or cause death. Any congenital anomaly will be included as follows definition of congenital abnormalities in Surveillance of Congenital Anomalies by Division of Birth Defects and Developmental Disabilities, NCBDDD, Centers for Disease Control and Prevention (2020).

  25. NICU admission

    Time frame: Up to delivery

    The admission of the newborn to the NICU.

  26. Neonatal mortality

    Time frame: Up to delivery

    Death of a live-born baby within 28 days of birth. This can be divided into early neonatal mortality, if death occurs in the first seven days after birth, and late neonatal if death occurs between 8 and 28 days after delivery.

Study contacts

Contact information is provided by the study sponsor or research team.

Tuong M Ho, MD

CONTACT

[email protected]

+84903633377

Xuyen Thi Ha Le, MD

CONTACT

[email protected]

+84945260494

Sponsors and collaborators

Lead sponsor

Mỹ Đức Hospital

Other

Collaborators

  • My Duc Phu Nhuan Hospital HCMC, Vietnam

Registry information

Official study title

Effects Of Endometrial Preparation Protocols On Peristalsis And Pregnancy Rates In Frozen Embryo Transfer: A Prospective Cohort Study

Acronym: EPFE

Important dates

Study start
2026
Primary completion
2026
Study completion
2027
First posted
Jan 22, 2026
Registry last updated
Mar 18, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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