Oocyte Survival After Vitrification With Slush Nitrogen Compared With Liquid Nitrogen


The purpose of this study is to determine if the use of slush nitrogen results in higher post-thaw survival rates for oocytes compared to conventionally used liquid nitrogen.

Study Type

  • Study Type: Interventional
  • Study Design
    • Allocation: Randomized
    • Intervention Model: Parallel Assignment
    • Primary Purpose: Basic Science
    • Masking: Single (Outcomes Assessor)
  • Study Primary Completion Date: August 31, 2020

Detailed Description

The study is a randomized, controlled trial which seeks to characterize oocyte survival rate following vitrification and subsequent warming with both slush nitrogen and liquid nitrogen. After warming, fertilization and embryology outcomes will be assessed.

Oocyte donors and a single donor sperm source will be utilized. Following enrollment, oocyte donors will undergo ovarian stimulation and oocyte retrieval. The mature (MII) oocytes obtained for each patient will then be assigned a number and randomized via block randomization to one of two treatment groups (liquid nitogen or slush nitrogen). Through block randomization, this will create a paired population of oocytes so that half of each patient's oocytes will undergo cryopreservation with liquid nitrogen and half will undergo cryopreservation with slush nitrogen. Timing of hyaluronidase stripping and vitrification will be consistent with current institutional clinical practice for oocytes.

Following cryopreservation, oocytes will be warmed and intracytoplasmic sperm injection will be performed and subsequent embryology outcomes tracked.


  • Other: Vitrification via slush nitrogen
    • oocytes will be vitrified using slush nitrogen
  • Other: Vitrification via liquid nitrogen
    • oocytes will be vitrified using liquid nitrogen which is currently routine practice

Arms, Groups and Cohorts

  • Active Comparator: Slush nitrogen
    • oocytes are randomized to undergo vitrification utilizing slush nitrogen
  • Active Comparator: Liquid Nitrogen
    • oocytes are randomized to undergo vitrification utilizing liquid nitrogen which is the current standard of care

Clinical Trial Outcome Measures

Primary Measures

  • oocyte survival rate
    • Time Frame: within 5 minutes post warming
    • number of viable oocytes post warming

Secondary Measures

  • fertilization rate
    • Time Frame: 18 hours post injection
    • number of zygotes post intracytoplasmic sperm injection procedure
  • blastulation rate
    • Time Frame: 4-6 days after fertilization
    • number of zygotes reaching the blastocyst stage of embryo development
  • euploid rate
    • Time Frame: 1 week after trophectoderm biopsy
    • number of chromosomally normal embryos

Participating in This Clinical Trial

Major Inclusion Criteria for oocyte donors:

1. Age 30 years or younger who meet institutional criteria to be an oocyte donor.

2. Patients who agree to donate oocytes for research purposes and agree to the study protocol.

3. The subgroup of oocyte donors age 35-38 will not be part of the primary analysis, and therefore will not be required to meet the age criteria listed above. The older group of donors will be chosen as the clinical discretion of the study investigators. No specific ovarian reserve cutoffs will be required, although factors related to ovarian reserve will be taken into consideration.

Major Exclusion Criteria for oocyte donors:

1. Under 18 years old

2. All patients who do not voluntarily give their written consent for participation.

3. Patients who do not meet standard institutional criteria for oocyte donation.

4. A diagnosis of polycystic ovarian syndrome (PCOS).

Gender Eligibility: Female

Minimum Age: 18 Years

Maximum Age: 30 Years

Are Healthy Volunteers Accepted: No

Investigator Details

  • Lead Sponsor
    • Reproductive Medicine Associates of New Jersey
  • Provider of Information About this Clinical Study
    • Sponsor
  • Overall Contact(s)
    • Christine V Whitehead, BSN, RN, 973-656-2841, clinicalresearchteam@ivirma.com

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