A transgender man who has given birth wants to be described to as the father of his child and not the mother as written in the child's birth certificate.
Freddy McConnell, who is a multimedia journalist at The Guardian, says being referred to as a mother was psychologically scarring.
Back in September, a judge ruled against him, after a High Court trial in London, but he has launched an appeal with three appeal judges now considering the case.
At the September ruling, Sir Andrew McFarlane, the president of the Family Division of the High Court and most senior family court judge in England and Wales, ruled against Mr. McConnell.
He concluded that people who had given birth were legally mothers, regardless of their gender, and said there was a 'material difference between a person's gender and their status as a parent'.
But Lord Burnett, the Lord Chief Justice and most senior judge in England and Wales, Lady Justice King and Lord Justice Singh have started analyzing case at a Court of Appeal.
The hearing is due to finish today.
A barrister leading Mr McConnell's legal team told the three judges at the Court of Appeal there were 'clear reasons' why her client should have won the High Court fight.
'Notwithstanding the complexity of the arguments and the issues engaged, there were clear reasons why the claim ought to have succeeded and why (Mr McConnell) ought to have been declared the father or parent of (the child), not the mother,' Hannah Markham QC stated in a written argument.
'It is submitted that the learned judge fell into error in determining the term 'mother' not to be a gendered term.'
She said Sir Andrew had failed to consider whether the current birth registration system was 'fit for purpose'.
'The learned judge was wrong to focus on giving birth as the determining issue when deciding parental role described in an administrative document,' she added.
'In identifying that the issue, in this case, raised important matters of public interest and that there was a pressing need for the government to challenge square on the status of a trans-male person who has become pregnant and given birth to a child, the learned judge ought to have declared where the current law fails to recognise those rights.