The objective was to understand experiences of double motherhood during antenatal, childbirth and postpartum healthcare, using a qualitative method involving individual online interviews and asynchronous, online focus groups of cisgender women, mostly in same-sex relationships. The results revealed how these women's experiences of parenting were marginalised, highlighting institutional violence in Brazilian healthcare services, which are presented here in two thematic dimensions: 1) Cisheteronormativity and its impact on experiences of double motherhood; and 2) Institutional violence in healthcare services: from curiosity to LGBTQIA+phobia. It was concluded that cisheteronormativity hinders healthcare for these experiences, especially by rendering the non-gestational mother invisible. This underscores the urgent need to train healthcare personnel, rethink and challenge cisgender and heterosexual norms and promote inclusive policies to ensure equitable care and combat institutional violence.