In Western societies, filiation is a social and legal construct. Two kinds of filiation exist, classical filiation, which rests in principle on biological engendering, and adoptive filiation, which is a purely legal construct. Filiation has long referred to the sexualised father/mother pattern. In France, twentieth-and twenty-first-century lawmakers have sought to adapt legal regulations on filiation to new reproductive techniques and to evolving wishes to have children, regardless of the family makeup. The law of 17 May 2013 (introducing "marriage for all") opened up adoption to same-sex married couples. The bioethics law of 2 August 2021 allows each partner in a female couple legally to become a mother through joint recognition: a third type of motherhood is thus created, which does not involve giving birth or an adoption order. Assisted reproductive technology (ART) is not open to male couples nor a priori to transgender persons. Legislation regarding filiation includes references to sex designation: the word "sex" appears three times in France's Civil Code: articles 57 (birth certificate), 61-5 (sex change) and 143 ("marriage for all"). In contrast, the word "gender" does not appear. Our legal construction of filiation does not address gender, a notion that has appeared more recently. Article 57 makes the designation of sex mandatory when a child's birth is registered. French legislation introduced on 18 November 2016 allows people to change the sex recorded on their birth certificate (Civil Code articles 61-5 to 61-8), without obligation of hormone treatment or sex-change surgery. The 2016 law considers that the change of sex has no effect on previous filiations, but does not address future filiations. Yet, if a transgender person has retained the sexual possibility to procreate, the question arises whether their wish to establish a gendered parentage should be recognised. Case study: On 16 September 2020, the Court of cassation examined the following affair: Mr X and Mrs Y were married in 1999 and gave birth to two children. In 2011, a court ruling allowed Mr X to obtain a change of sex on the civil register, while keeping their male sexual organs. In 2014, the couple had a third child. The genitor, now Mrs X, signed a pre-natal acknowledgement of parentage as a "non-gestational mother". The civil registrar refused to transcribe this recognition. The Court of cassation ruled in favour of this refusal, recalling that under French law a mother or father cannot be designated as "biological parent" in the civil registry and that it is not possible to establish a double maternal filiation (except in the case of adoption or, henceforth, through joint recognition of a child born of assisted procreation). Moreover, the child's best interest is preserved since their filiation may be established with both parents, enabling the third child to have the same filiation as their brethren born before the registration of sex-change. In a separate case, two men, one cisgender, the other transgender, registered the birth of a baby girl born of the transgender partner. The practical solution consisted in replacing "born of father and mother" on the birth certificate by "son or daughter of''. Yet, is sex assignation at birth justified? On 19 June 2019, a ruling of the Belgian Constitutional Court censured the Belgian law of 25 June 2017 allowing the civil registration of sex-change for limiting this possibility to a binary choice and considering it irrevocable. ???C 2022 Elsevier Masson SAS. All rights reserved.
