P-766 Re-assessment of the Belgian legislation on embryo transfer in a blastocyst transfer policy

Abstract Study question How does a multiple fresh blastocyst transfer policy impacts live birth rate (LBR) and rates (MLBR) in relation to maternal age ? Summary answer Fresh transferring of ≥ 2 blastocysts only increases LBR women above the 36 substantially risk multiples all categories. What is known already Multiple pregnancies after ART are recognized as major complication it significantly contributes extreme preterm very low-birthweight births. Even presence strict Belgian embryo law some subgroups which double (DET) allowed (women aged <36 years cycle rank 3 up 6 36-40 2), twining remain 10%. A study by Tannus et al., (2017) concluded that (DBT) associated with both higher twin compared elective single (eSBT). design, size, duration center retrospective, observational cohort was conducted between July 2010 December 2020. Both IVF ICSI cycles were included. total 8,402 transfers performed (2,948 on day 5,454 5) over course period. SET 6,108 cases, DET 2,077 triple (TET) 202 cases (MET) 15 cases. Participants/materials, setting, methods The primary outcomes this per pregnancy rate. Generalized estimating equations (GEE) patient subject applied account for clustering within women. An interaction analysis number embryos transferred categories 5 group performed. P-value < 0.05 considered statistically significant. Main results role chance In years, chances not when two or more vs. (OR: 1.014; 95%% CI 0.791 - 1.299; p = 0.91). However, than one >40 did result SBT 1.631; 95% CI: 1.218 2.185; 0.0008 OR: 1.634; 1.219-2.190; 0.0008, respectively).` Women > 40 had an estimated 19.3% 66.3% lower odds respectively embryo, 0.800, 0.687-0.931; 0.0034 0.337, 0.268-0.424; 0.0001, respectively). Overall, births 28.5% 1.285 1.1.077 – 1.533) (p 0.0046). 17.8 times DBT/MBT (OR 17.814; 10.74 29.55) 0.0001). Limitations, reasons caution This limited its retrospective design no possible due low twins. Wider implications findings data indicates younger should be regardless quality rank. Only patients older blastocyst(s) could considered. Trial registration Not applicable