['We retrospectively examined a large cohort of females who underwent single blastocyst transfer to determine if initial β-human chorionic gonadotrophin (β-hCG) levels on day 7 after single vitrified-warmed blastocyst transfer (SVBT) could be used to predict pregnancy outcome.', 'The treatment cycles that gave rise to the early pregnancies included in this study were performed from 2004 to 2011 in a private infertility center. In SVBT cycles, embryos were transferred during a natural cycle or after endometrial preparation with exogenous estrogen and progesterone. A total of 11,458 cycles with β-hCG levels ≥1.0 UI/ml on day 7 after SVBT were evaluated. The proportion of live births per positive β-hCG cycle was established for 10 β-hCG ranges in 3 different age groups (Group A: 21-34 years old; Group B: 35-39 years old; Group C: 40-44 years old).', 'The proportion of live births gradually increased from 1.5 to 93.7%, 0.8 to 87.9%, and 0.6 to 76.2% in Groups A, B, and C, respectively. For each range of β-hCG levels, the proportion of live births was higher for the younger age group, which reflected the increased risk of early pregnancy loss with advancing female age.'] Do maternal age and initial β-hCG levels predict pregnancy outcome after single vitrified-warmed blastocyst transfer?