Employers must not discriminate against an employee because she is undergoing IVF, but only in relation to the period between egg collection and implantation of the fresh embryos.
An employee is only protected from discrimination on grounds of pregnancy once embryos are implanted. Prior to that, an employee subjected to detriment because she is undergoing IVF treatment will be able to claim sex discrimination without having to point to a male comparator treated more favourably (eg in relation to time off), but only in relation to the period between egg collection and implantation of fresh embryos (and not any frozen embryos implanted subsequently).
The EAT considered that this special protection does not apply to the period prior to egg collection, nor to any other gender-specific illnesses.
This ruling was not necessary to decide the case. It takes a narrow interpretation of the ECJ decision in Mayr and could well be challenged in the future. (Sahota v Home Office, EAT)