Improving IVF Success Rates: Using Low Oxygen in the Lab

Paramount to the success of an IVF cycle is the IVF laboratory handling the gametes and embryos. While an IVF laboratory can’t turn a poor quality egg or sperm into a good quality embryo (at least not yet), they certainly can create conditions that result in a good egg or sperm yielding a poor quality embryo. Thus, when looking at IVF programs, select a program that has a cutting edge laboratory using optimal conditions to foster embryo growth.

Like many things in life, there is more than one way to accomplish the same endpoint within an IVF lab. However, there are a few key “best practices” for successful embryo growth, and use of low oxygen levels in the incubator is clearly one.

In the modern embryo culture system, use of low oxygen is essential. Culturing embryos in reduced oxygen concentrations (~5%), compared to atmospheric concentrations of ~21%, has long been recognized as superior in various animal IVF systems [1-7]. This makes sense when one considers the female reproductive tract appears to have oxygen levels between 2-8% (see reviews [5, 8]). Numerous studies have also demonstrated improved human embryo development, implantation, and pregnancy rates when using reduced oxygen concentrations [9-21]. Admittedly, confounding variables in some studies can make direct comparisons difficult. However, it is difficult to identify a study that demonstrates a detriment to using low oxygen for growing embryos. Importantly, use of low oxygen throughout the entire culture period of 5-6 days appears to be required to see the most benefit [9, 11, 12].

One of the better designed studies — a prospective randomized controlled trial at a high-performing program — showed that use of low oxygen significantly improved pregnancy, implantation and live birth rates [11]. Embryos cultured under low oxygen resulted in almost a 15% increase in live birth. Similar improvements of ~10-18% in live birth have been reported by others using low oxygen [12,22] and confirmed via a Cochrane review and meta-analysis [23, 24].

This is important to know because not all IVF labs have the capability to use low oxygen culture. This requires specialized incubators and or gas supply. In a web-based survey of embryologists, it was noted that more than 31% of IVF labs in North America were not using low oxygen culture conditions in their incubators to grow embryos [25]. This means you have approximately a 1 in 3 chance of selecting an IVF clinic that is not using the optimal low oxygen culture conditions. Only ~24% of labs surveyed were using low oxygen conditions exclusively.

So, when looking for an IVF center, in addition to looking at success rates and ensuring you’ll like the physician/nurses, make sure to ask about growth conditions used in the lab as well.

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