The Human Fertilisation and Embryology Authority (HFEA) is the body responsible for overseeing fertility services in the UK.  They currently have a traffic light system that evaluates evidence for additional treatments that may be offered to you if you undergo fertility treatment.  They only use evidence from randomised control trials (RCTs) in their system and they only use a live birth (giving birth to a baby at the end of the treatment) as a way of defining success. In RCTs, a particular drug, food, or other intervention is tested for the effect it has in one group where a control group that isn’t treated is monitored alongside the study group.