To understand the full extent of the impact of a trial, it is important to consider the long-term consequences of outcomes beyond the trial follow-up period, especially for early year’s interventions. A systematic review of the literature associated with the long-term consequences of four key outcomes from the Building Blocks trial, specifically, low birth weight, smoking during pregnancy, interval to subsequent pregnancy and A&E attendance or inpatient admission was conducted. These factors were guided by the funders, the Department of Health, as being of particular interest in the UK context. Relevant studies were identified from a number of sources including large databases, reference checking and citation searching. The search yielded 3665 papers, 43 of which were considered appropriate for inclusion. Of these, 29 were relating to smoking during pregnancy, 13 to low birth weight, 0 to A&E attendances during early childhood and 1 to short (< 2 years) interval to subsequent pregnancy. Consistent associations were found between maternal smoking during pregnancy and the effects this has on children’s health, educational attainment and likelihood of engaging in problem behaviour and criminal activity in later life. Low birth weight was also found to impact on children’s long-term health and cognitive development. Subsequent pregnancies within two years of the previous birth were linked with increased likelihood of pre-term birth and neonatal death. Only minimal evidence was identified regarding the consequences of a short interval to second pregnancy and of child A&E and outpatient attendances. Given that these outcomes have been identified by the UK Department of Health as of particular interest for UK benefit, investment of research in these areas is recommended to establish a clearer picture of both short and long-term consequences.