The clinical outcome of Ultra-low oxygen tension on post thawed human blastocyst

In vitro, Embryo development depends on several factors as temperature, pH, and oxygen in the surrounding environment of the embryo. Impaired culture conditions are highly correlated with poor embryo development. Oxygen is a powerful regulator of embryo function , as it is responsible for cell respiration, energy production and rapid cell growth . Increased levels of oxygen is associated with an increase in the levels of ROS , which leads to unfavorable culture conditions, as it might affect the stability of cell membrane, DNA, and protein function .

In the female reproductive tract, oxygen concentration fluctuates between 2-8%, which is considered to be at its highest level in the fallopian tube, while the lowest level is in the uterus . Pre-implantation embryo crosses the uterotubal junction after the time of compaction on Day 3, where it is exposed to a shift in oxygen tension to 2%. This variation may have a role in the metabolic reactions of the embryo, and in its preparation for implantation process.

Some studies suggested that culturing embryos with oxygen tension below 5% may have an embryological advantage mimicking nature.

Embryological laboratories routinely use low Oxygen tension (5%). Our purpose is to investigate if ultra-low oxygen tension (2%) has an advantage over low oxygen tension (5%) for post thawed human embryo regarding clinical outcomes.

Inclusion Criteria:

Single or Multiple Embryo transfer embryo transfer. Female age 18-40. Embryo vitrified on day 5 or day 6 of insemination.

Exclusion Criteria:

Use of sperm donation. Use of Oocyte donation. Use of gestational carrier. Uterine congenital anomalies. Presence of any of the endometrial factors that affect embryo implantation such as hydrosalpings, adenomyosis or previously known uterine infection.

Any contradictions to undergoing in vitro fertilization or gonadotropin stimulation.