As our understanding of genetics has grown, and its importance has increased in clinical care, pregnancy and the fetus are often seen through a genetic lens. Clinicians who care for pregnant women are charged with explaining genetic risk and overseeing prenatal screening. For the clinician, genetics represents clearly defined application of a particular kind of scientific knowledge. Further, heritability in clinical terms is understood as purely genetic. Pregnant women themselves, however, may not give these genetic explanations the same primacy or meaning. In order to better understand the way pregnant women actually understand and explain heritability, we completed in-depth interviews with 26 pregnant women, listening as they gave weight and substance to the various factors they describe as influencing the personhood of their unborn children. Two-thirds of our respondents were Hispanic or African American. Most were recruited through programs that serve low-income women. The interviews were coded and analyzed by using categories that emerged directly from the narratives captured in the interviews and that revealed the broad, cross-cutting, overlapping parameters of women's deeply-held beliefs about heritability. These stories represent narratives of heritability that are profoundly familial and cultural. They incorporate belief in the authoritative knowledge of medicine—including any genetic information—into a complex and usually multicultural context, woven together by ancestry, household, and community.