Background: Early motherhood has been linked with a number of adverse outcomes, including mental health difficulties and barriers to completing educational qualifications and workforce participation. The present study examined the extent to which these linkages could be explained by the influence of social, family, and background factors that were associated with early motherhood. Methods: Data were gathered as part of the Christchurch Health and Development Study, a 25-year longitudinal study of a birth cohort of New Zealand children. Information was obtained on: (a) the history of pregnancy and parenthood for female participants over the period 15-21 years; (b) measures of DSM-IV mental disorders and suicidal behaviour over the interval 21-25 years; (c) measures of educational achievement over the interval 21-25 years; (d) measures of welfare dependence, workforce participation, and income over the interval 21-25 years; and (e) childhood, family and related confounding factors. Results: Early motherhood was associated with higher levels of mental health disorders, lower levels of educational achievement, higher levels of welfare dependence, lower levels of workforce participation, and lower income. Control for confounding factors reduced the associations between early motherhood and later mental health disorders to statistical non-significance. However, the associations between early motherhood and later educational achievement and economic circumstances persisted after control for potentially confounding factors. Conclusions: The findings suggest that early motherhood puts young women at risk for educational underachievement and poorer economic circumstances. The linkages between early motherhood and later mental health difficulties can largely be accounted for by childhood, family, and related circumstances that occurred prior to parenthood.