What is the effect of embryo morphology on serum β-hCG levels?

To determine the effect of embryonic factors on serum beta human chorionic gonadotropin (β-hCG) levels in pregnancy and live birth resulting after a single fresh cleavage embryo and blastocyst transfer.

This was a retrospective cohort study conducted at a tertiary care hospital. All fresh single embryo transfers (sETs) between September 2011 and December 2016 were included. The correlation analysis was performed to determine the association of embryo morphological parameters on mean serum β-hCG levels on day 12 after the transfer of a fresh single cleavage embryo and a fresh single blastocyst embryo.

Out of a total of 455 fresh sETs, 60 positive β-hCG results after the transfer of a single fresh cleavage-stage embryo and 82 after the transfer of a single fresh blastocyst. The mean β-hCG level resulting from a single fresh blastocyst ET was 371.7 ± 52.7 IU/L, which was similar to the mean β-hCG level resulting from a cleavage ET (314.5 ± 36.9 IU/L) (p = .70). Interestingly, serum β-hCG levels resulting from a single fresh blastocyst ET showed a correlation with day 5 blastocoele expansion, trophectoderm cell number and blastocyst quality score in ongoing pregnancy (r = .33, p = .02; r = .29, p = .04; and r = .31, p = .03, respectively). Moreover, day 5 blastocoele expansion and blastocyst quality score showed a correlation with the serum β-hCG levels resulting from a single fresh blastocyst ET in live birth (r = .36, p = .02; r = .31, p = .04, respectively).

Our study suggests that serum β-hCG levels resulting from a single fresh blastocyst ET showed a correlation with day 5 blastocoele expansion and blastocyst quality score in both ongoing pregnancy and live birth.