RESUMEN
OBJECTIVE: To determine threshold ß-hCG levels predictive of an ongoing pregnancy (OP), live birth (LB), and multiple gestation (MG) in IVF cycles resulting from day-3 (D3) vs. day-5 (D5) embryo transfers (ET), to compare IVF cycle characteristics and pregnancy outcomes in D3 vs. D5 ET groups, and to assess the degree to which maternal characteristics and cycle parameters were predictive of higher ß-hCG levels. DESIGN: Retrospective analysis. SETTING: Infertility center. PATIENT(S): Women who had ET performed for IVF cycles between July 2004 and January 2010. INTERVENTION(S): Embryo transfer performed on either D3 or D5 after oocyte fertilization. MAIN OUTCOME MEASURE(S): Beta-hCG on day 15 after oocyte fertilization. RESULT(S): Beta-hCG levels were significantly higher with D5 ET compared with D3 ETs (D3: 103.6 ± 4.4 IU/L vs. D5: 198.0 ± 10.6 IU/L), and a multivariate analysis demonstrated that D5 ET was a significant predictor of higher ß-hCG levels. The ß-hCG thresholds predictive of OP were 78 IU/L and 160 IU/L for D3 and D5 ET, which predicted OP in 96% and 91% of cases, respectively. Similarly, for LB, the ß-hCG thresholds were 94 IU/L (79% positive predictive value [PPV]) and 160 IU/L (88% PPV), and for MG were 250 IU/L (18% PPV) and 316 IU/L (34% PPV), respectively. CONCLUSION(S): Initial ß-hCG levels are dependent on the day of ET and are a reliable and highly predictive tool for OP outcomes.