RESUMEN
OBJECTIVE(S): Beta human chorionic gonadotrophin (ß-hCG) is secreted by placenta and detectable in maternal serum a few days after embryo implantation. The evolution of ß-hCG serum levels is commonly used to confirm early pregnancy and differentiate normal pregnancies from others, either in spontaneous pregnancies or after IVF. However, little is known on the eventual link between blastocyst quality in IVF, pregnancy outcome, and ßhCG kinetics. The objective was to evaluate the association between early ßhCG rise, blastocyst morphology and pregnancy evolution in a single-blastocyst transfer program STUDY DESIGN: This retrospective cohort study was conducted in a University-affiliated IVF center in 441 couples undergoing 455 single blastocyst transfer cycles leading to a positive pregnancy test 12â¯days afterwards. The rate of rise of ß-hCG (ß-hCG kinetics) was calculated in each cycle and its association with blastocyst quality and pregnancy clinical outcome was evaluated. RESULTS: ß-hCG kinetics was significantly different according to blastocyst expansion, but with considerable overlap between groups. ß-hCG kinetics was also significantly different according to clinical outcome, with higher values in clinical pregnancies than in other groups. This remained true in subgroups' analysis according to blastocyst expansion and in top quality blastocysts. CONCLUSION(S): Early ß-hCG kinetics after single-blastocyst transfer is different according to pregnancy outcome and is only slightly influenced by blastocyst quality. These results confirm the interest of ß-hCG follow up in IVF pregnancies, and do not support the interest of building blastocyst-specific ß-hCG ranges in IVF cycles.