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.