A transgender man who has given birth but does not want to be described as "mother" on a birth certificate has begun the next round of a legal battle.
Freddy McConnell, a multimedia journalist who works for The Guardian, wants to be registered as father or parent.
A judge ruled against him after a High Court trial in London, but he has launched an appeal.
Three appeal judges, including the most senior judge in England and Wales, are considering the case.
Sir Andrew McFarlane, the president of the Family Division of the High Court and the most senior family court judge in England and Wales, ruled against Mr McConnell in September.
He concluded that people who had given birth were legally mothers, regardless of their gender.
Lord Chief Justice Lord Burnett, Lady Justice King and Lord Justice Singh are analysing arguments at a Court of Appeal hearing in London.
The hearing is due to end on Thursday.
Sir Andrew heard that Mr McConnell was a single parent who was born a woman but now lives as a man following surgery.
He had been biologically able to get pregnant and give birth but had legally become a man when the child was born.
He wanted to be registered as father or parent but a registrar told him the law required people who give birth to be registered as mothers.
He took legal action against the General Register Office, which administers the registration of births and deaths in England and Wales.
Sir Andrew concluded there was a "material difference between a person's gender and their status as a parent".
