In FZ v MZ [2025] EWHC 3338 (Fam), the High Court considered the parental status of a trans man, FZ, whose partner, MZ, conceived two children using donor insemination after FZ had obtained a Gender Recognition Certificate (“GRC”).

FZ and MZ met in 2020. FZ, who was assigned female at birth, received his GRC in 2021 and they married in 2022. During their relationship but before marrying, MZ underwent artificial insemination, outside of a licensed clinic, with a known sperm donor, XX. The couple’s first child, DZ, was born in 2023. Subsequently, in 2024, using the same process and donor, but after marriage, MZ gave birth to a second child, AZ.

The local registry initially registered FZ as DZ’s “father” but all parties accepted that this was incorrect. The couple were not married at conception and DZ failed to satisfy the requirements, in Human Fertilisation and Embryology Act 2008 (“HFEA 2008”), sections 36 and 37, for an unmarried man to become a father. At common law, XX, as the genetic progenitor, was the father of DZ. Lieven J. issued a declaration that FZ was not the father of DZ (at [25]–[29]) and made a step-parent adoption order for FZ concerning DZ (at [30]–[37]). Lacking any statutory power to order re-registration, the judge quashed the initial birth certificate and allowed DZ’s birth to be registered anew.

Lieven J. also concluded that FZ could not be registered as AZ’s “father” under HFEA 2008, section 35. Applying the reasoning from R. (on the Application of McConnell) v The Registrar General for England and Wales [2020] EWCA Civ 559, [2021] Fam. 77 (“McConnell”), the judge noted that – although, due to his GRC, FZ had married MZ as a man before conception – Gender Recognition Act 2004 (“GRA 2004”), section 12, ousted the GRC’s effects in relation to FZ’s “status […] as the father or mother of a child” (at [68]–[76] (emphasis added)). As GRA 2004, section 12, treated FZ as a woman for the purposes of parental status, he could not become the “father” of AZ through HFEA 2008, section 35 – which was restricted to married men.

Moreover, because GRA 2004, section 12, only affected parenthood, not marital status, Lieven J. held that, within the HFEA, FZ and MZ were in a different-sex marriage. Consequently, in addition to HFEA 2008, section 35, not applying, FZ was also excluded from HFEA 2008, section 42, the equivalent provision allowing a woman to become the second “female” parent, because he was not a woman married to the mother of AZ (at [107]). Therefore, FZ had no statutory right to be registered as either the father or second female parent of AZ.

Lieven J. acknowledged that this interfered with FZ and AZ’s rights to respect for private and family life under European Convention on Human Rights (“ECHR”), Article 8(1) (at [82]–[83]). However, the restriction was clearly provided for in primary legislation (at [84]) and expressly pursued what Lieven J. considered as “capable of being” a legitimate aim (at [97]): “to exclude the status of parenthood […] from the legal effect of having obtained a GRC” (at [95]). In reviewing proportionality, the judgment suggested that the parental status of trans individuals raised important policy judgements, which were more appropriately determined by Parliament (at [98]). Granting lawmakers a wide margin of judgement, Lieven J. concluded that ousting the GRC’s effects from legal parenthood was rationally connected to a legitimate aim, was the least intrusive means available and struck a fair balance between competing interests (at [103]–[108]). Thus, there was no violation of ECHR, Article 8.

The judgment in FZ v MZ gives rise to several important reflections. First, the approach to statutory interpretation means that neither HFEA 2008, section 35 nor section 42 can be satisfied by trans men with GRCs. The reasoning follows McConnell, finding that GRA 2004, section 12, disapplies the GRC for the purposes of HFEA 2008, section 35, so that FZ could not be registered as AZ’s “father”. However, Lieven J. went further than this application of McConnell – finding that GRA 2004, section 12 does not apply to HFEA 2008, section 42, meaning that the GRC applies for the purposes of that provision. The judgment’s explanation for this is very brief (at [107]), particularly given its significance, but the distinction appears to be based upon HFEA 2008, section 42, requiring marriage or civil partnership between the mother and “another woman” – which a trans man with a GRC cannot be. The reasoning’s brevity means that Lieven J. does not explain why GRA 2004, section 12 would not also disapply the GRC for the purposes of parental status under HFEA 2008, section 42. This would have allowed FZ’s recognition as the second female “parent”. The result is a form of “Schrödinger’s GRC”: legal gender recognition (“LGR”) applies to prevent legal parenthood for trans men with GRCs under HFEA 2008, section 42, while simultaneously not applying to prevent those men from becoming parents under HFEA 2008, section 35. Thus, the judgment treats the GRC differently between these provisions despite their “mirror” functions – allowing legal parenthood for the male and female spouse or civil partner of the “mother” – within the HFEA 2008.

Second, there are various questions about how Lieven J. undertook her human rights analysis. The judge concluded that any interference with the parties’ ECHR, Article 8 rights pursued a legitimate aim: excluding the GRC’s effects when determining parental status. Yet, it is unclear whether this goal expresses an aim or merely a result. In McConnell, it was held that Parliament required registration according to birth sex in order to ensure a coherent administrative system and to protect the rights of children. Irrespective of the merits, ousting the GRC in McConnell had defined policy and rights objectives. However, in FZ v MZ, Lieven J. appeared to identify registration according to birth sex as a legitimate aim in itself. Adopting a highly deferential approach, the judgment offered little analysis of what (if any) policy or rights goals a fully sex-based registration system pursues. Therefore, it remains unclear against what “legitimate aim” FZ and AZ’s rights were being balanced. The judgment does refer to maintaining the “determinative” role of biological sex (at [97]). Yet, it is equally uncertain how or why this aim should be relevant to HFEA 2008, section 35 when, as Lieven J. acknowledges, the sexed body of a married man, including his gametes, plays no role in determining his legal status as father under that provision.

The decision’s treatment of the concepts of fair balance and least restrictive means raises further concerns. Regarding the former, Lieven J. gives limited acknowledgement to the fact that, due to the ruling, FZ is denied any parental status regarding AZ (at [107]–[108]). This outcome constitutes a highly significant interference with respect for FZ’s family life and differentiates this litigation from both McConnell and the prior European Court of Human Rights jurisprudence (e.g. AH v Germany (2026) 82 E.H.R.R. 1, at [132]; Hamalainen v Finland (2014) 37 B.H.R.C. 55, at [86]) – which, even when ruling against trans parents, emphasised the ability to establish and maintain parental status. Lieven J.’s references to the mitigatory effects of parental responsibility and orders under Children Act 1989, section 8 are unconvincing – overlooking the practical and symbolic importance of legal parenthood. Furthermore, it is not obvious why fully excluding FZ from legal parenthood was the least restrictive means of curbing his ECHR, Article 8 rights. While application of HFEA 2008, section 42 would not be consistent with FZ’s gender identity (at [104]), it would have afforded him parental status and there was nothing in the judgment to indicate that FZ actively objected to registration as a second female “parent”.

Moreover, Lieven J. chose not to engage with ECHR, Article 14 reasoning that any potential interference would be permissible for the same reasons justifying the interference with ECHR, Article 8 (at [109]). This approach is regrettable, obscuring the clear discrimination, on the sole basis of gender identity, between trans men with GRCs and non-trans men to whom HFEA 2008, section 35 applies. It also ignores the unequal treatment experienced by some trans men, as compared with trans male peers, simply because they exercise their ECHR right to obtain LGR. While trans men without a GRC can be registered under HFEA 2008, section 42, FZ v MZ absolutely excludes trans men who have accessed LGR from becoming legal parents using donor sperm.

Finally, Lieven J. described For Women Scotland v the Scottish Ministers [2025] UKSC 16, [2026] A.C. 315 (“FWS”) as “of limited direct relevance” (at [61]) because that decision considered the relationship between GRA 2004, section 9 and the Equality Act 2010, rather than the HFEA 2008. However, we have previously argued (A. Brown and P. Dunne, “The Family Law Implications and Consequences of For Women Scotland” [2025] Family Law 1191) that the Supreme Court’s reasoning on GRA 2004, section 9(3) strongly indicates that gendered terms in HFEA 2008 should also be read as referring to “biological women” and “biological men” (FWS, at [103]–[108]). Consequently, we suggested “there is no role for s[ection] 12 of the GRA in determining the parental status of trans people under the ‘parenthood provisions’ of the [HFEA 2008]” (at 1197). Applying this reasoning to FZ v MZ would not have had the effect of denying FZ any parental status. If HFEA 2008, section 42 applied to “biological woman”, this would have allowed FZ’s recognition as a second female “parent”. Therefore, this provides a different route through which FZ could have become a legal parent.

Overall, the judgment in FZ v MZ contains questionable statutory interpretation and flawed human rights analysis. It would be hugely disappointing for trans parents if this represents the final word on this issue.