Natural Versus Programmed Frozen Embryo Transfer (NatPro) (NatPro)

  • End date
    Sep 30, 2024
  • participants needed
  • sponsor
    JHSPH Center for Clinical Trials
Updated on 4 October 2022
body mass index
Accepts healthy volunteers


NatPro is a two-arm, parallel-group, multi-center, randomized trial in which women undergoing frozen embryo transfer (FET) will be randomized to receive either a modified natural cycle (corpus luteum present) or a programmed cycle (corpus luteum absent).


NatPro is a two-arm, parallel-group, multi-center, randomized trial in which women undergoing FET will be randomized to receive either a modified natural cycle (corpus luteum present) or a programmed cycle (corpus luteum absent). The study will implement a stratified randomization design to balance the use of pre-implantation genetic testing (PGT) across the two treatment arms. Each participant will have up to 3 FET cycles until live birth occurs, or the participant has no embryos available for transfer. Primary endpoints will be the proportion of women experiencing preeclampsia comparing modified natural to programmed FET among women with viable pregnancy (defined as pregnancy lasting at least 20 weeks) and the cumulative proportion of women having live births in the two arms.

Condition Pregnancy Related, Pre-Eclampsia
Treatment Modified natural cycle, Programmed cycle
Clinical Study IdentifierNCT04551807
SponsorJHSPH Center for Clinical Trials
Last Modified on4 October 2022


Yes No Not Sure

Inclusion Criteria

To be eligible, subjects must meet all these criteria
Age 18-39 years at the time that embryos were created if no PGT testing was performed. If PGT testing was performed and indicates that an embryo is euploid, the patient can be included if she was age 18-41 years at the time that the embryo was created
Age 18-41 years at the time of randomization as advancing age itself becomes a significant risk for preeclampsia
Normal uterine cavity as assessed by saline infusion sonohysterogram, hysterosalpingogram, or hysteroscopy within one year of the enrollment visit, and repeated at the discretion of the investigator
Regular menstrual cycle length (approximately 24-35 days) indicative of ovulatory cycles
Willing to undergo elective single embryo transfer
Body Mass Index <=40
Prior to enrollment, participant will have at least one vitrified blastocyst with euploid result by pre-implantation genetic testing (PGT-A) or at least one vitrified blastocyst of fair or better morphologic quality if no PGT-A results are available
Willingness to be randomized to either a modified natural or programmed cycle, with a willingness to administer intramuscular progesterone in oil if assigned to the programmed cycle
Normal thyroid stimulating hormone (TSH), according to local laboratory standards (or TSH level with a clinically insignificant abnormality per the site director), within one year of study enrollment and repeated at the discretion of the investigator. Use of thyroid medication is permitted

Exclusion Criteria

To be eligible, subjects must not meet any one of these criteria
Medical contraindication to pregnancy
Embryos created using donor oocytes
Embryo donation
Gestational carrier
Reciprocal IVF (one female partner carrying pregnancy, other female partner as source of eggs)
Fresh embryos created from frozen oocytes. Patients with frozen embryos created from frozen oocytes can be included
Recurrent implantation failure defined as no clinical pregnancy with ≥ 2 prior consecutive embryo transfers unless patient also had successful live birth between or after the failed embryo transfers
Anti-phospholipid antibody syndrome or rheumatologic disease requiring chronic systemic medications
Uncontrolled diabetes mellitus
History of >1 pregnancy loss in the second or third trimester
Uncontrolled hypertension
Untreated hydrosalpinx (i.e., hydrosalpinx in situ which has not been ligated or removed)
Physician recommendation to perform the embryo transfer outside of the timing specified by the protocol
Mullerian uterine anomaly, if not correctable
Contraindication to any medication which must be used in preparation for the frozen embryo transfer (i.e., estradiol, progesterone, hCG)
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If you are confirmed eligible after full screening, you will be required to understand and sign the informed consent if you decide to enroll in the study. Once enrolled you may be asked to make scheduled visits over a period of time.

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