IVF embryos may thrive when grown with less oxygen 

Lowering the oxygen levels that embryos are exposed to during IVF improves fetal and placental development, according to a study in mice. This is thought to be due to low oxygen levels better mimicking the conditions of the reproductive tract.

https://www.newscientist.com/article/2580792-ivf-embryos-may-thrive-when-grown-with-less-oxygen/