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

Multi-center, Parallel-group, Randomized Controlled Trial of Modified Natural Versus Programmed Cycles for Frozen Embryo Transfers and Their Association With Preeclampsia and Live Births

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).

Study Overview

• Status: Active, not recruiting
• Conditions: Pregnancy Related; Pre-Eclampsia
• Intervention / Treatment: Procedure: Modified natural cycle; Procedure: Programmed cycle

Detailed Description

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.

• Study Type: Interventional
• Enrollment (Actual): 788
• Phase: Phase 3

Contacts and Locations

Study Locations

• United States
  • California
    • San Francisco, California, United States, 94158
      • University of California San Francisco
    • Sunnyvale, California, United States, 94087
      • Stanford University
  • Connecticut
    • Orange, Connecticut, United States, 06477
      • Yale
  • Hawaii
    • Honolulu, Hawaii, United States, 96814
      • Fertility Institute of Hawaii
  • Illinois
    • Chicago, Illinois, United States, 60611
      • Northwestern University
  • Maryland
    • Baltimore, Maryland, United States, 21093
      • Johns Hopkins
    • Rockville, Maryland, United States, 20850
      • Shady Grove Fertility
  • Massachusetts
    • Waltham, Massachusetts, United States, 02451
      • Boston IVF
  • New York
    • Rochester, New York, United States, 14642
      • University of Rochester
  • North Carolina
    • Charlotte, North Carolina, United States, 28203
      • Atrium Health
  • Ohio
    • Beachwood, Ohio, United States, 44122
      • Cleveland Clinic Foundation
  • Oklahoma
    • Oklahoma City, Oklahoma, United States, 73104
      • University of Oklahoma
  • Pennsylvania
    • Philadelphia, Pennsylvania, United States, 19104
      • University of Pennsylvania
  • Texas
    • Bedford, Texas, United States, 76022
      • Care Fertility
  • West Virginia
    • Morgantown, West Virginia, United States, 26505
      • West Virginia University Center for Reproductive Medicine

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 41 years (Adult)
• Accepts Healthy Volunteers: Yes

Description

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
• If Body Mass Index is over 30 or individual has other risk factors for diabetes, normal hemoglobin A1C
• 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)
• Mullerian uterine anomaly, if not correctable
• Physician recommendation to perform the embryo transfer outside of the timing specified by the protocol
• Contraindication to any medication which must be used in preparation for the frozen embryo transfer (i.e., estradiol, progesterone, hCG)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Modified natural cycle; corpus luteum present	Procedure: Modified natural cycle; This treatment protocol is defined as a modified natural cycle as the participant will be instructed to (1) administer human chorionic gonadotropin (hCG) to assist with timing of the embryo transfer and (2) supplement the luteal phase with a low dose of progesterone.
Active Comparator: Programmed cycle; corpus luteum absent	Procedure: Programmed cycle; This protocol is designated as programmed because the endometrial development occurs only in association with administration of estradiol and progesterone. No ovulation occurs due to suppression of follicle development by the estradiol and the timing of the transfer is based on the number of days elapsed following initiation of exogenous progesterone.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Preeclampsia	Frequency of preeclampsia, as defined by American College of Obstetricians and Gynecologists (ACOG) guidelines for hypertensive disorders in pregnancy (Obstetrics & Gynecology 2020;135:e237-e260)	During pregnancy through the post-partum period, according to ACOG guidelines (typically between 20 weeks gestation and 6 weeks post-delivery)

Collaborators and Investigators

• Sponsor: JHSPH Center for Clinical Trials
• Investigators: Principal Investigator: Valerie Baker, MD, Department of Gynecology and Obstetrics, Johns Hopkins School of Medicine; Principal Investigator: James Segars, MD, Department of Gynecology and Obstetrics, Johns Hopkins School of Medicine

Publications and helpful links

General Publications

• Baksh S, Casper A, Christianson MS, Devine K, Doody KJ, Ehrhardt S, Hansen KR, Lathi RB, Timbo F, Usadi R, Vitek W, Shade DM, Segars J, Baker VL; NatPro Study Group. Natural vs. programmed cycles for frozen embryo transfer: study protocol for an investigator-initiated, randomized, controlled, multicenter clinical trial. Trials. 2021 Sep 27;22(1):660. doi: 10.1186/s13063-021-05637-3.

Study record dates

Study Major Dates

• Study Start (Actual): September 16, 2020
• Primary Completion (Estimated): February 1, 2026
• Study Completion (Estimated): April 1, 2026

Study Registration Dates

• First Submitted: August 27, 2020
• First Submitted That Met QC Criteria: September 15, 2020
• First Posted (Actual): September 16, 2020

Study Record Updates

• Last Update Posted (Actual): May 16, 2025
• Last Update Submitted That Met QC Criteria: May 15, 2025
• Last Verified: May 1, 2025

More Information

Terms related to this study

• Keywords: infertility; in vitro fertilization; frozen embryo transfer
• Additional Relevant MeSH Terms: Urogenital Diseases; Female Urogenital Diseases and Pregnancy Complications; Pregnancy Complications; Hypertension, Pregnancy-Induced; Eclampsia; Pre-Eclampsia
• Other Study ID Numbers: IRB00214688

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No