High initial β-hCG predicts IVF outcomes accurately and precludes the need for repeated measurements.

This study evaluated β-human chorionic gonadotropin (hCG) changes during the early period of pregnancy in an attempt to predict successful pregnancy outcomes in ART. It determined the median values of the β-hCG and the 2-day β-hCG increments of clinical vs biochemical pregnancies. The results of fresh day 3 embryo, frozen day 3 embryo, and frozen day 5 embryo transfers were evaluated. The cutoff values of β-hCG and the 2-day increments predicting clinical pregnancy and delivery were determined. All women who underwent embryo transfer and had a singleton pregnancy from January 2017 to December 2019 were included. As expected, clinical pregnancies had higher initial median β-hCG values compared to biochemical pregnancies (fresh day 3 (400 vs 73 mIU/mL), frozen day 3 (600 vs 268.5 mIU/mL) and frozen day 5 (937 vs 317 mIU/mL)). Nonetheless, the abortion rate was significantly lower in the group with β-hCG above the cutoff values in fresh (141 mIU/mL) and frozen (354.5 mIU/mL) cleavage stage transfers (17.2% vs 44%, P < 0.001 and 18.5% vs 38%, P = 0.003, respectively). Blastocyst transfers resulted in higher median initial β-hCG compared to cleavage embryo transfers (937 vs 600 mIU/mL), and the initial β-hCG values from frozen cleavage embryos were higher compared to fresh cleavage embryos (600 vs 400 mIU/mL). Earlier implantation in frozen cycles may be caused by freezing-thawing procedures. Moreover, in fresh cycles, negative effects of the hormonal milieu of fresh cycles may delay implantation. These results indicate that high initial β-hCG and high 2-day β-hCG increments demonstrated better outcomes, including more clinical pregnancies and fewer abortions.