Fertility add-ons are treatments offered by UK fertility clinics claiming to boost the chances of having a successful pregnancy or baby. They are optional extras that are offered on top of normal fertility treatment and usually at an additional cost. Add-ons are highly controversial because, despite being emerging techniques with little or no proven evidence of success, the use of them in clinical practice has increased exponentially. These can range from £50 for a single screening blood test to as much as £8,000 for egg freezing packages.