ABSTRACT
ObjectivesTo assess the correlation between blastocyst morphology score， serum human chorionic gonadotropin β subunit （β-hCG） levels on day 12 after transfer and live birth outcomes among cycles tested HCG-positive after thawed single blastocyst transfer； to analyze the predictive value of serum β-hCG levels on live birth. MethodsWe reviewed the data of 519 frozen-thawed single blastocyst transfer cycles （FET） that had been tested HCG-positive from January 2016 to May 2020 at our IVF center. These FET cycles were firstly divided into 4 groups （AA， AB， BA， and BB） according to Gardner's grading system of inner cell mass （ICM） and trophectoderm cell （TE）， and then 4 groups （stages 3， 4， 5 and 6） according to the degree of blastocyst expansion. Serum β-hCG concentrations on day 12 after transfer and live birth rates were compared among groups transferred with different blastocysts grading and expansion stage. The relationship between Gardner’s grading or expansion stage of blastocysts and serum β-hCG levels was determined by correlation test， and ROC curves were plotted to determine the threshold values of serum β-hCG for predicting live birth. Results（1） The serum β-hCG concentration in the AA group and AB group on the 12th day after the transfer was significantly higher than that in the BB group （P <0.001， P <0.001）. However， there was no significant difference in the live birth rate when different ICM/TE-graded blastocysts were transferred （P = 0.120）. There were no significant differences in serum β-hCG concentration on day 12 after transfer and live birth rate among blastocysts with different expansion stages （P = 0.091， P = 0.557）. （2） There was a significant weak correlation between blastocyst ICM/TE grading and serum β-hCG concentration on day 12 （rs = -0.221， P <0.001）， and even after controlling for confounding factors （ rs = -0.228， P <0.001）；There was no significant correlation between blastocyst’s expansion stage and serum β-hCG concentration on day 12 after the transfer （rs = -0.052， P = 0.240）， and the association remained insignificant after controlling for confounding factors （rs = -0.029， P = 0.508）. （3） ROC curve analysis showed that the cut-off value for predicting live birth by serum β-hCG on day 12 was 657.5 mU/mL （P < 0.001）. ConclusionsNeither the ICM/TE grade nor the expansion stage of blastocysts affect the live birth rate，there is significant difference in the level of β-hCG produced by blastocyst with different ICM/TE grade；Our results suggest that early serum β-hCG level can predict live birth.