PROJECT SUMMARY Research linking unintended pregnancy with increased risk of adverse maternal and child health outcomes is fraught with significant conceptual and scientific limitations, including cross-sectional designs, residual confounding, and simplistic, retrospective assessment of pregnancy intentions. A critical gap in our scientific knowledge thus remains: Are the adverse maternal health outcomes associated with unintended pregnancy and childbearing due to unintended pregnancy itself or rather contextual factors that are associated with increased risk of unintended pregnancy? The proposed research is the first to apply state-of-the-art methods and theory to the measurement of pregnancy intentions to rigorously address this long-standing scientific gap. This prospective study follows a cohort of 2,200 non-pregnant women over one year, measuring preferences about a possible pregnancy using a new, robust instrument: the Desire to Avoid Pregnancy (DAP) scale. This validated psychometric scale captures a continuum of cognitive, affective, and practical considerations about pregnancy and childbearing, moving beyond conceptually limited “intending” and “not intending” labels. Participants experiencing incident pregnancies – and a matched subset of non-pregnant women with similar pregnancy preferences – are then followed for an additional three years to measure mental and physical health outcomes during pregnancy and after birth. This innovative design positions us to address three aims. In Aim 1, we will identify the time-varying and invariant contextual factors in women’s lives that shape their preconception pregnancy preferences, such as relationship factors and financial stability, and test how preferences predict incident pregnancy. In Aim 2, among women who experience a new pregnancy, we will examine the relationship between prospectively assessed pregnancy preferences and maternal health outcomes, accounting for temporally important confounding factors (from Aim 1). In Aim 3, we will investigate how the relationship between pregnancy and adverse health outcomes differs by pregnancy preferences. Specifically, with our matched design, we will compare health outcomes among pregnant women to those of women who best represent their counterfactual: women who had similar pregnancy preferences yet who did not experience pregnancy. Thereby, we emulate a hypothetic trial in which women, conditional on confounders, are randomly assigned to pregnancy, allowing us to examine whether the negative health effects of pregnancy are amplified among those who most desire to avoid pregnancy. Achieving these aims will contribute new insights into the health repercussions of unintended pregnancy for women and elucidate the degree to which adverse outcomes stem from the intention status of pregnancies or underlying social and contextual factors. These insights are critical to developing appropriately focused maternal morbidity prevention efforts. Robust data on h...