The behavioral and biological underpinnings of family planning (FP) unfold on an individual level, across a full reproductive lifecourse, and within a complex system of social and structural constraints. Yet, much of the existing FP modeling landscape hasfocused solely on macro- or population-level dynamics of family planning. There is a need for an individual-based approach toprovide a deeper understanding of how family planning is intertwined with individuals’lives and health at the micro-level, whichcan contribute to more effective, person-centered design of both contraceptive technologies and programmatic interventions. Thisarticle introduces the Family Planning Simulator (FPsim), a data-driven, agent-based model of family planning, which explicitlymodels individual heterogeneity in biology and behavior over the life course. Agents in FPsim can experience a wide range of life-course events, such as increases in fecundability (and primary infertility), sexual debut, contraceptive choice, postpartum familyplanning, abortion, miscarriage, stillbirth, infant mortality, and maternal mortality. The core components of the model—fecundability and contraceptive choice, are represented individually and probabilistically, following age-specific patterns observedin demographic data and prospective cohort studies. Once calibrated to a setting leveraging multiple sources of data, FPsim can beused to build hypothetical scenarios and interrogate counterfactual research questions about the use, non-use, and/or efficacy offamily planning programs and contraceptive methods. To our knowledge, FPsim is the first open-source, individual-level, woman-centered model of family planning.
