Association between seven-day serum β-hCG levels after frozen–thawed embryo transfer and pregnancy outcomes: a single-centre retrospective study from China

Objective: Early monitoring of plasma human chorionic
gonadotropin (β-hCG) level is vital in predicting pregnancy outcome. This
study investigated the predictive value of serum β-hCG level on the 7th
day after frozen-thawed embryo transfer (FET) for ongoing pregnancy (OP)
and adverse pregnancy (AP). Design: Retrospective study
Setting: The Reproductive and Genetic Center of the Affiliated
Hospital of Shandong University of Traditional Chinese Medicine, China.
Participants: 1,061 pregnant women who underwent FET between January 2014
and January 2017.   Primary and secondary outcome measures:
Pregnancy outcome. Results: Serum β-hCG levels on the 7th day after FET
were higher in the single OP group compared to the biochemical pregnancy
(BP) group (p ＜0.001). Besides, the serum β-hCG cutoff level at 4.34
mIU/mL on the 7th day showed high predictive value (area under the curve
[AUC] = 0.852). Serum β-hCG levels on the 7th day after FET were higher in
the twin OP group compared to the single OP group (p＜0.001). Also, the
serum β-hCG cutoff level at 17.95 mIU/mL on the 7th day showed high
predictive value (AUC = 0.903). Serum β-hCG levels on the 7th day after
FET were lower in the ectopic pregnancy (EP) group compared to the single
OP group (p ＜0.001) whereas, serum β-hCG cutoff level at 4.53 mIU/mL on
the 7th day exhibited a high predictive value (AUC = 0.860). Further, the
serum β-hCG levels on the 7th day after FET were lower in the single early
spontaneous abortion (SA) group compared to the single OP group (p＜0.001)
while the serum β-hCG cutoff level at 5.34 mIU/mL on the 7th day exhibited
high predictive value (AUC = 0.738). Conclusion: Serum β-hCG on
the 7th day after FET has good clinical significance for the prediction of
OP and AP.