Intimate partner relationships are evolving, and non-cohabiting couples are attracting growing research interest. However, few studies have focused on parenthood in this context. Applying a new set of union categories, the 2016 National Perinatal Survey sheds light on the social profiles and childbearing trajectories of women in non-cohabiting unions at the time of childbirth. Are they different from lone mothers? Are these births planned? This research note uses statistical analysis to examine this group of women, long overlooked in major surveys. At variance with dominant norms, mothers in non-cohabiting unions represent 3% of births in France. They form a diverse population that includes very young women, often still in education, along with older women of foreign origin who are generally more highly educated and more often in employment than lone mothers. In terms of pregnancy planning and antenatal care, women in non-cohabiting unions are in an intermediate position: they receive more antenatal care than lone mothers, but monitoring is less regular than for mothers in cohabiting unions, often because they take longer to realize that they are pregnant. This suggests that these births are often unexpected rather than unwanted.