A Controlled Randomized Trial Evaluating the Effect of Lowered Incubator Oxygen Tension on Live Births in a Predominantly Blastocyst Transfer Program

Purpose: The purpose of this study is to determine if a more physiological oxygen concentration (5%) will improve clinical outcomes when compared with the industry standard of 21%.

Background: For embryos to grow in the incubator, atmospheric gas concentrations should be as close to possible to those seen in the oviduct or uterus. Currently, atmospheric (non-physiological, 21%) oxygen concentrations are used in the incubators to culture the embryos of infertility patients of the Presbyterian ARTS laboratories. Literature suggest that culturing animal embryos in a reduced oxygen environment will significantly improve embryo quality and clinical outcomes. Both 5% and atmospheric oxygen concentrations are routinely used for embryo culture in the human IVF laboratories, however, very few commercial human IVF facilities invest in oxygen control as it is more expensive to maintain and labor intensive to implement. The goal is to use lower oxygen concentrations in the future if clinical improvement justifies the expense and increased labor associated with low oxygen culture.

Project Summary: Study design: The study will be conducted in a prospective, randomized way. Two treatment groups are considered: 1) existing atmospheric oxygen concentration in embryo incubators 2) lower 5% oxygen concentration in embryo culture incubators. To allow for the well-documented decline in pregnancy rates with increased age, patients will be stratified within 4 age groups and 3 physicians within each treatment. The age groups are: donor eggs; <35 years; 35 to 37 years; and 38 to 40 years as determined on the day of egg retrieval.

Endpoints Measured: The endpoints measured will be embryo cryopreservation-biochemical pregnancy-, clinical pregnancy-, ongoing pregnancy-, live birth- and embryo implantation rates.

Number of Patients in the Study: To detect a difference of 10% in pregnancy rates, 150 patients should be included in each treatment group. With the current patient volume, it should take less than one year to complete the study. Differences in implantation rates may be detected earlier (more embryos transferred than patients enrolled). Should significance differences in pregnancy rates become evident before the full number of patients is enrolled, the study may be terminated.