Abstract
Pregnancy requires dynamic physiological adaptation across multiple biological systems implicated in perinatal mental health. Researchers increasingly recognize the importance of social and structural determinants of maternal mental health, yet integrating these conditions with molecular research remains challenging. A biosocial approach builds on these efforts by asking what conditions – both biological and social – contribute to the molecular variation we observe. In this Perspective, we use allopregnanolone (ALLO), a progesterone-derived neuroactive steroid implicated in perinatal mental health, to illustrate this approach. Evidence reviewed here shows that ALLO is patterned across social and physiological contexts, while associations between ALLO and depression, anxiety, and psychosocial distress during pregnancy remain heterogeneous. These observations highlight two priorities for biosocial molecular research: better characterization of the contexts in which molecular variation occurs and direct testing of what those contexts contribute to our understanding of ALLO in perinatal mental health. A biosocial approach does not replace biological explanation with social explanation; it asks whether better characterization of both changes what we observe. This means measuring social experiences alongside physiological characteristics, then asking whether these conditions contribute to ALLO variation or shape its associations with psychosocial distress. Such approaches can investigate how adversity becomes biologically embodied and how supportive conditions may promote maternal adaptation and well-being. Recognizing biological plasticity is central to this work: molecular variation can reflect dynamic responses to ongoing conditions rather than fixed characteristics of individuals or populations. Molecular variation should not be treated as the endpoint of inquiry, but as a starting point.