Abstract Objective The purpose of the study is to contribute to an understanding of the cultural and normative meaning of birth motherhood and how lesbian couples decide who carries the child. Background The decision of who carries the child is central in lesbian family‐making, carrying consequences for life after birth. Even so, it has been relatively overlooked in research. Drawing from the sociology of personal life and Park's (2013) conceptualization of monomaternalism, we study how informants consider and decide birth motherhood. Method Semistructured interviews with both partners in 21 pregnant lesbian couples in the Netherlands were thematically analyzed. Results The meaning of birth motherhood was ambivalent, linked to femininity, socially recognized motherhood, and biogenetic imaginaries. In couples where both wanted to carry, age, which carried different symbolic meanings, was a powerful tiebreaker. Conclusion Our study shows how the monomaternalist norm shapes conceptualizations of birth motherhood. Desires to experience pregnancy are strong for many. Referring to age can be a way for couples to defuse tension, but it can also be a resource drawn upon to close further negotiations. Implications Our study carries implications for policy makers, health care workers, and mothers‐to‐be. Scholarly, it illuminates the ways in which motherhood, in its various forms, is perceived and recognized.