What families need to know about birth registration, assisted reproduction and legal parenthood following the decision in FZ v MZ [2025].
The facts behind the decision
The recent case of FZ v MZ [2025] EWHC 3338 concerned a married couple and their two young children. FZ is a transgender man who received a Gender Recognition Certificate (GRC) in 2021. This means he is legally recognised as a male. FZ married his wife, MZ, who is the biological and gestational mother of the children, in 2022.
Both children were conceived using artificial insemination with sperm from a known donor, arranged privately rather than through a licensed fertility clinic. The older child, D, was conceived in the summer of 2022, before the parties were married. The younger child, K, was conceived in 2023 after they were married.
FZ and MZ live together, share the care of both children and present as a typical mother-and-father family. However, they faced difficulties when it came to registering the children’s births and determining who the law recognised as their legal parents.
What the law tells us
The Gender Recognition Act 2004 states that when someone receives a GRC, their acquired gender becomes their legal gender “for all purposes.” However, section 12 of the Act excludes a person’s acquired gender from affecting their status as the father or mother of a child and states that a trans person must be recorded on the birth certificate by way of their birth sex.
The rules on legal parenthood following assisted reproduction are set out in the Human Fertilisation and Embryology Act 2008. It states that the woman who carries the child is always treated as the legal mother. Section 35 of the Act states that where a woman undergoes artificial insemination and is married at the time, the man to whom she is married will be treated as the child’s legal father, provided he consented to the treatment.
Another relevant piece of legislation is the Family Law Act 1986, which allows the court to make declarations of parentage to confirm whether someone is, or is not, a legal parent.
FZ argued that because he was legally male and married to MZ when K was conceived, he should be treated as K’s father under the 2008 Act and registered on the birth certificate. In relation to D, FZ argued that his name should not be entirely removed from K’s birth certificate.
The court’s decision
The judge disagreed with FZ’s reasoning. She held that the rule which treats a married man as a child’s father is about a person’s legal status as a parent. Parliament has expressly stated in the GRC that acquiring a new legal gender does not change that parental status. As a result, FZ could not rely on his GRC to bring himself within the assisted reproduction provisions that apply to married men.
The court accepted that this decision affected the family’s right to respect for private and family life but did not consider that there had been a breach of FZ’s rights under Article 8 of the European Convention of Human Rights. The court concluded that Parliament has deliberately drawn this boundary and that decisions about how parenthood is recorded involve sensitive social and ethical issues that are for Parliament, not the courts, to resolve.
The court made a child arrangements order so that FZ would share parental responsibility for K and continue to care for him, but it refused to declare that FZ was K’s legal father. This means that FZ cannot be named as K’s father on his birth certificate. In practice, this may mean having to provide explanations or additional paperwork when dealing with schools, doctors or other organisations. It also means that K’s official identity record does not reflect the family life that the parties are living today.
The outcome was different for the older child, D. As D was conceived before the parties were married and outside a licensed clinic, the 2008 Act did not apply, and common law rules treated the sperm donor as D’s legal father. The court also allowed the judicial review claim to quash the original birth registration. Originally, FZ had been incorrectly registered as D’s father, so the local authority subsequently notified the parties that this was a mistake. The court therefore made a declaration that FZ was not D’s legal parent and allowed the original birth registration to be cancelled and redone, so that the error was no longer on the public register.
To reflect the reality of family life, the court also made a step-parent adoption order, replacing the sperm donor with FZ as D’s legal father. This meant that FZ ultimately became D’s father, even though he could not be recognised as K’s father in the same way.
What the court’s decision means for families
The court’s decision in this case shows that the law does not always reflect the reality for modern families. Even where parents are married and raising children together, legal recognition can depend on factors such as whether conception took place in a licensed clinic or whether the parents were married at the time. For transgender parents and for families using private fertility arrangements, the legal position can be unexpected and deeply personal. Taking legal advice at an early stage can help families understand how the law will treat parenthood and what steps may be needed to ensure their family is legally protected.
If you have any queries regarding legal parenthood or any other aspects of family law, please contact a member of the Field Seymour Parkes family team.
Article contributor, Liya Khwaja, Paralegal
