Maternal β-HCG concentrations in early IVF pregnancy: association with the embryo development stage of blastocysts

Does the blastocyst development stage on embryo transfer day affect serum β-human chorionic gonadotrophin (β-HCG) concentration 9 and 16 days after embryo transfer in women whose pregnancy progresses beyond 13 weeks?

Retrospective study involving 204 cases where pregnancy progressed beyond 13 weeks of single blastocyst transfer in fresh (n = 66) or frozen embryo transfer (FET) (n = 138) cycles from January 2015 to September 2016.

β-HCG concentrations 9 and 16 days after embryo transfer in FET cycles (median 223 IU/l and 4378 IU/l, respectively) were significantly (P < 0.001) higher than in fresh cycles (157 IU/l and 2813 IU/l). Among fresh cycles, faster-growing blastocysts (expanded + hatching + hatched blastocysts) produced significantly (P < 0.001) higher β-HCG concentrations 9 days after embryo transfer (191 IU/l) than slower-growing blastocysts (cavitating + full blastocyst, 106 IU/l); however no significant difference was found between the faster- and slower-growing groups by day 16 (2359 IU/l and 3025 IU/l, respectively). Among FET cycles, there was no difference in β-HCG concentration between blastocysts of different development stages 9 and 16 days after transfer.

Faster-growing blastocysts produced significantly higher serum β-HCG concentrations 9 days after transfer than slower-growing blastocysts in fresh cycles, but the difference was not significant by day 16 after transfer. Also, β-HCG concentrations 9 and 16 days after embryo transfer in FET cycles were higher than in fresh embryo transfer cycles. Interpretation of β-HCG results 9 days after blastocyst transfer should consider the blastocyst growth rate and whether fresh or cryopreserved embryo was transferred.