In this thesis, the relationships that lesbian couples negotiate on the path to first-time parenthood are explored. The analysis draws on interviews with 48 lesbian mothers-to-be (both partners in 24 lesbian couples), as well as data from Dutch population registers, to study the transition to parenthood. Two relationships are the focus of this thesis: the relationship between the two future mothers, and the relationship between the future family and the donor. Both are characterized by roles that are in a state of cultural flux. Motherhood and mothering take on new meanings when performed in relation to another mother, rather than a father. At the same time, the cultural figure of the sperm donor has evolved drastically over recent decades. These relationships are also infused with economic and transactional considerations. Transitioning to motherhood has been shown to be associated with economic penalties across time and country contexts. Whether, and how, this matters for assigning birth motherhood in lesbian couples has received little research attention to date. The donor-parent relationship is constituted through a specific type of exchange. This exchange may be mediated through sperm banks or established through negotiations between donors and parents themselves in informal sperm donation. In these relationships, the cultural and economic must be reconciled. Following Zelizer’s theoretical approach on connected lives, I argue that this reconciliation is achieved through relational work. The thesis comprises four papers that, together, highlight different facets of relational work. Study 1 explores how lesbian mothers-to-be think about the desirability of birth motherhood and how they come to the decision regarding who will carry the child, drawing from qualitative interviews. Views on the desirability of birth motherhood are multilayered and complex. Conflicting desires between partners (e.g., when both want to carry the child) are often resolved by invoking age norms associated with motherhood. Study 2 reconsiders how female same-sex couples assign birth motherhood when transitioning to parenthood, using Dutch register data on 1959 female same-sex couples who became parents between 2007 and 2016. Linear probability models show that partners’ relative wages and employment characteristics—such as working hours and sector or industry of employment—influence which partner carries the child. Study 3, returning to the interview data, examines how the pluriform conceptive practices of lesbian couples relate to their envisioned future family relationships. Drawing from the kinning perspective, I consider how choices regarding clinical or non-clinical insemination, a contact or sperm bank donor, and technological interventions can affirm the non-birth mother’s future role, and shape the relationship between the donor and the future family. Study 4 investigates how lesbian couples build trust with contact donors when engaging in informal sperm donation. Relying on the interview data, I find that contracts, social networks, and signaling—trust resources well-established in the literature—all play a role in building trust. However, I also explore how informants and evaluate these different strategies for building trust, finding that the meaning informants attribute to the relationship matters for how informants present and talk about trust resources.