Evaluation of the Impact of Reduced Oxygen Concentration on Embryonic Development
Trial Snapshot
- Phase
- Not Applicable
- Status
- Completed
- Enrollment
- 60
- Locations
- 2
- Primary Endpoint
- Blastulation Rate (number of embryos meeting criteria for biopsy and/cryopreservation divided by number of embryos randomized on day 3 to either the experimental or control arm)
Study Overview
Brief Summary
During this study, patients will undergo a routine in vitro fertilization cycle as they would otherwise if not participating in the study. After eggs have been fertilized they will be cultured as usual until day 3 of embryo development. On day 3 of development, the embryologist will randomize half of the embryos to be cultured in 2% oxygen concentration and the other half at 5%, which is currently the standard of care. All other embryological care procedures will remain the same. On day 5 or 6 of embryo development, the embryos will be evaluated and each blastocyst stage embryo will be recorded. The primary outcome will be the blastulation rate (or percentage of embryos that reach the blastocyst stage).
Detailed Description
Significant progress has been made in characterizing the optimal environment for a developing embryo in culture. These efforts have been based on the premise that clinical embryo culture should mimic the in vivo environment. To this end, investigators have gone to great lengths to recreate every aspect of the natural setting to which the early embryo is exposed. This focused approach has led to significant modifications of the embryo culture system in the modern in vitro fertilization (IVF) lab and ultimately to improvements in pregnancy rates.
One area that has been subject to significant scrutiny is the relationship between incubator oxygen concentration and early embryonic development. Oxygen plays a central role in embryonic metabolism. The mechanism governing its utilization is dependent on the stage of embryonic development. During the first 3 days of development, oxygen reaches the embryo via passive diffusion and its concentration gradient is regulated by oxygen consumption during oxidative phosphorylation. Inefficiencies in this process - due to compromised integrity of the inner mitochondrial membrane or alterations in substrate availability - can result in excessive production of harmful reactive oxygen species which can cause significant damage to cellular machinery and ultimately lead to embryonic arrest.
The concentration of oxygen that the embryo in culture is exposed to can also impact this delicately balanced system and alter the metabolic health of an embryo. Historically, atmospheric oxygen concentration (approximately 20%) was exclusively used in human IVF laboratories for embryo culture. However, multiple investigations subsequently found that the physiologic concentration of oxygen within the female reproductive tract is well below atmospheric levels, being consistently measured at <10%. These observations led to multiple trials comparing atmospheric oxygen concentrations to 5% oxygen in embryo culture. These studies demonstrated significant perturbations in gene expression, protein secretion, and suboptimal utilization of amino acids and carbohydrates in embryos cultured in atmospheric oxygen. The same comparisons were made in clinical IVF studies and demonstrated that embryos cultured in 5% oxygen consistently resulted in an increase in clinical pregnancy rate and live birth rate. A meta-analysis of this topic suggested that a clinic with a baseline live birth rate of 30% could expect an improvement as great as 13% when culturing embryos at 5% O2.
As a result of these compelling data, most modern IVF programs now exclusively culture embryos at 5% oxygen concentration. However, some have proposed that the oxygen concentration to which the embryo is exposed after day 3 of development is actually lower than 5%. These data originate from the idea that the embryo crosses the utero-tubal junction on day 3 of development in vivo. Multiple studies have demonstrated that the oxygen concentration in the uterus is actually lower than that in the fallopian tube at approximately 2%. Thus, the most physiologic embryo culture system would culture embryos in 5% oxygen until day 3 and then decrease the oxygen concentration to 2% until transfer or cryopreservation on day 5 or 6.
A change in the optimal oxygen concentration for an embryo on day 3 would fit with a general shift in metabolic requirements of embryos seen at this stage of development. Activation of the embryonic genome occurs on day 3 which prompts a significant increase in biosynthetic activity. The metabolic behavior of embryos also shifts substantially during this time. The embryo changes its metabolic strategy from oxidative phosphorylation to glucose based metabolism in the form of the aerobic glycolysis and the citric acid cycle. During this process, termed compaction, embryos exhibit greatly increased oxygen consumption.
Study Design
- Study Type
- Interventional
- Allocation
- Randomized
- Intervention Model
- Single Group
- Primary Purpose
- Treatment
- Masking
- Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Eligibility Criteria
- Ages
- 18 Years to 40 Years (Adult)
- Sex
- Female
- Accepts Healthy Volunteers
- Yes
Inclusion Criteria
- •Age 18-40 years and seeking IVF with aneuploidy screening, which is our current recommendation regardless of study participation
- •Anti-mullerian hormone level (AMH) > 1.0 pmol/L (an assessment of ovarian reserve)
- •Must have at least two surviving embryos on day 3 of development
- •Male partner with >100,000 total motile spermatozoa per ejaculate (donor sperm acceptable)
- •Body Mass Index < 35
Exclusion Criteria
- •Diagnosis of endometrial insufficiency, as defined by prior cycle with maximal endometrial thickness <6mm, abnormal endometrial pattern (failure to attain a trilaminar appearance), or persistent endometrial fluid
- •Use of oocyte donation
- •Use of gestational carrier
- •Use of sperm obtained via surgical procedure
- •Presence of hydrosalpinges that communicate with endometrial cavity
- •Single gene disorders, chromosomal translocations or any other disorders requiring more detailed embryo genetic analysis
- •Couples seeking gender selection for family balancing
Arms & Interventions
2% oxygen concentration in the incubator
At the time that embryos are changed from "cleavage stage media" to "blastocyst stage media" on day 3 of development, half of a given patient's embryos will randomly be placed in an incubator set at 2% oxygen concentration. The splitting of the embryos will be done under low magnification such that the embryologist will have no ability to bias allocation of embryos to 2% or 5% oxygen based on embryo morphology on day 3. The embryos will remain in this incubator until their developmental assessments on day 5 and 6.
Intervention: 2% oxygen concentration in the incubator (Other)
Control
Embryos in this arm will be cultured at 5% oxygen (current standard of care) from day 3 until blastocyst developmental assessment.
Outcomes
Primary Outcomes
Blastulation Rate (number of embryos meeting criteria for biopsy and/cryopreservation divided by number of embryos randomized on day 3 to either the experimental or control arm)
Time Frame: 6 days of embryonic development in the laboratory
On day 5 and day 6, all embryos are examined under the microscope to see if they 1) meet developmental criteria for embryo biopsy (for chromosomal evaluation) and cryopreservation (since all embryos in this program are cryopreserved while awaiting results from chromosome assessment), or 2) arrest development in the laboratory.
Secondary Outcomes
- Clinical Pregnancy rate(2 months)