 Multiple pregnancy MP is associated with significant fetomaternal complications and a high cost. The multiple pregnancy rate per cycle MPR of treatment with Assisted Reproductive Technology ART is 25 or higher even in countries where ART is reimbursed, much higher than the 1 after natural conception, related to the number of embryos transferred, and preventable by single embryo transfer SET. In Belgium, the laboratory costs for 6 fresh ART cycles are reimbursed for female patients younger than 43 with a Belgian insurance number since July 2003, but only if a limited number of embryos is transferred depending on female age and cycle rank. Although this policy has resulted in a significant reduction in the MPR after ART in Belgium from 24 to 13 , available data are cycle based and it is unknown if the cumulative delivery rate per patient is affected by this legislation. The aim of this study was to test the hypothesis that Belgian ART legislation since 2003, coupling lab reimbursement to restriced embryo transfer policy, has resulted in a reduced CDR when compared to the situation before 2003. 