Skip to main content
OpenTrials
Recruiting

NCT Number: NCT07675213

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

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.

Recruiting

Interested in participating?

Request Info

Key information

Age range

18 year–42 year

Sex eligibility

Female

Study type

Observational

Primary location

About this study

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.

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
  • 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

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

Treatment and study plan

Endometrial peristalsis and hormone measurements

Other

Time 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.

Primary outcomes

  1. The correlation between endometrial peristalsis at different time points and live birth rates

    Time frame: Up to delivery

    The correlation between endometrial peristalsis at different time points and live birth rates

Secondary outcomes

  1. The frequency of 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 (before progesterone exposure) • On the day of embryo transfer, immediately prior to the procedure

    The frequency of endometrial peristalsis at different time points

  2. 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 (before progesterone exposure) • On the day of embryo transfer, immediately prior to the procedure

    The correlation between endometrial peristalsis at different time points

  3. 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 (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)

  4. 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

  5. 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

  6. Positive pregnancy test

    Time frame: 10-14 days after embryo transfer

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

  7. 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

  8. 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

  9. 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)

  10. Ectopic pregnancy

    Time frame: Up to 12 weeks after embryo transfer

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

  11. 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

  12. Multiple gestations

    Time frame: At delivery

    A pregnancy with more than one embryo or fetus

  13. 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

  14. Mode of delivery

    Time frame: At delivery

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

  15. Birth weight

    Time frame: At delivery

    Weight of the newborn measured right after delivery

  16. Gestational age at birth

    Time frame: At delivery

    Calculated by gestational age of all live births

  17. 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

  18. 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

  19. 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

  20. 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

  21. Very low birth weight

    Time frame: Up to delivery

    Birth weight less than 1.500 g

  22. Low birth weight

    Time frame: Up to delivery

    Birth weight less than 2.500 g

  23. 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

  24. 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

  25. 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)

  26. NICU admission

    Time frame: Up to delivery

    The admission of the newborn to the NICU

  27. 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.

Nhi NL Ho, MD

CONTACT

[email protected]

+84903497611

Vu NA Ho, MD, PhD

CONTACT

[email protected]

+84935843336

Sponsors and collaborators

Lead sponsor

Mỹ Đức Hospital

Other

Registry information

Official study title

Correlation Between Endometrial Peristalsis And Pregnancy Outcomes In Patients Undergoing Frozen Embryo Transfer With Hormone Replacement Therapy for Endometrial Preparation Protocol

Acronym: CONCO

Important dates

Study start
2026
Primary completion
2027
Study completion
2027
First posted
Jun 30, 2026
Registry last updated
Jul 9, 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.

Published trials that share one or more normalized conditions with this study.