INTRODUCTION Higher adult socioeconomic position (SEP) is associated with better birth outcomes. However, few studies incorporate life-course or intergenerational SEP, which may inform etiology and targeted prevention efforts. This study tested whether life-course social mobility from childhood was associated with lower risk of adverse birth outcomes. METHODS Data were from the Life-course Influences of Fetal Environments (LIFE) retrospective cohort study among black women, 2009-2011, in metropolitan Detroit, MI. This study (analyzed in 2014-2016) examined whether social mobility was associated with two primary birth outcomes: small for gestational age (SGA) and preterm birth (PTB). Childhood and adulthood SEP were measured by survey in adulthood, for two constructs, measured ordinally: educational attainment and perceived financial sufficiency (subjective income/wealth). Social mobility was calculated as the difference of adulthood minus childhood SEP. RESULTS In covariate-adjusted Poisson regression models, 1-SD improved educational social mobility from childhood to adulthood was protective for SGA (adjusted risk ratio=0.76; 95% CI=0.64, 0.91); this association remained after adjusting for financial mobility. Upward financial social mobility from early childhood was marginally protective for SGA (adjusted risk ratio=0.85; 95% CI=0.72, 1.02), but became nonsignificant after controlling educational mobility. There were no overall associations of social mobility with PTB or low birth weight, although sensitivity analyses identified that improved financial mobility was associated with 16% marginally lower risk of spontaneous PTB and 28% marginally lower risk of low birth weight among upwardly mobile/stable women only. CONCLUSIONS Improved life-course social mobility is associated with reduced risk for SGA and spontaneous PTB among black women.