Background <p>Evidence on how policy interventions early in childhood can prevent or delay multiple long-term conditions (MLTCs) is limited. We modelled prevention scenarios using five early-life domains on the outcome of MLTCs with role-limitation using effectiveness data of combined real-life early interventions.</p> Methods <p>Our study sample was 6201 participants in the 1970 British Cohort Study. The outcome was MLTCs with role-limitation (i.e. impacting everyday life functioning) as reported by participants at age 46. We constructed adversity scores within early-life domains (from prenatal to age 10) including prenatal to birth, developmental attributes, education, socioeconomic factors and family environment and used adjusted multivariable logistic regression to examine their relationship with the outcome. We generated adjusted population attribution fractions to estimate the reduction in outcome risk if cohort members reduced their adversity scores. Using effect estimates on early-life exposures from evaluations of real-life interventions including Family Hubs, the Family Nurse Partnership and the teenage pregnancy prevention framework, we calculated the absolute reduction in the outcome risk had cohort members been exposed to all three interventions.</p> Results <p>Reducing early life adversity scores from 3 + to 1, from 3 + to 0, from 2 to 0 in the developmental attributes domain and from 3 + to 2, from 3 + to 0, from 1 to 0 in the prenatal to birth domain, lowered the outcome risk. For the developmental attributes domain, the combined effect of the interventions could result in a 0.5% reduction in MLTCs with role limitations for those with a domain adversity score of 3 +. For the prenatal-birth domain, the combined effect of the interventions could result in a 11.5% and 2.5% reduction in MLTCs with role limitations for those with a domain adversity score of 3 + and 1, respectively.</p> Conclusions <p>Interventions during pregnancy, the postnatal period and childhood may reduce MLTC risk in midlife.</p>