OBJECTIVES: We have examined the impact of long term disability costs arising from increased use of IVF treatments in relation to multiple births reductions in Canada. METHODS: Using the Canadian Fertility Cost Model we estimated the potential cost savings of reducing the number of multiple pregnancies in Canada. A series of probabilistic analyses were performed to account for the effect of uncertainty in long-term outcomes and disability costs on the cost effectiveness of reducing multiple births.  Values for disability rates were sampled from a beta distribution and costs were sampled from a log-normal distribution. Simulation results were generated by simultaneously varying long-term disability rates and costs. The outcomes included age-specific net total costs, lifetime disability costs, and incremental costs per live birth. RESULTS: Assuming reductions in multiple birth rates equal to those reached by selected European countries, we estimated that, over the next five years in Canada, the multiple birth rates could be reduced from 28.8% to 13.4%. Using Monte-Carlo simulations, the potential cost savings range from $150 million to $558 million, and the reduction in over-all incremental cost per live birth range from $8,560 to $31,897. The proportions of children with lifetime disabilities range from 6.0% to 24.0% for current practice, and 4.3% to 17.3% assuming reductions in multiple births. For women under 35, aged 35-39, and over 40, reductions in over-all incremental cost range from ($9,555 - $35,616), ($7,814 - $29,977) and ($6,031 - $22,543), respectively. The bulk of cost reductions (ranging from 50% to 87%) would be attributable to reductions in disability costs. CONCLUSIONS: Our analysis shows that a reduction in multiple births would result in potential cost savings.  The amount of variation in the long term outcomes and disability costs make the projections, nevertheless, highly unstable.