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

<p><span><b><span>Objective:</span></b> 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). </span></p> <p><span><b><span>Design: </span></b>Retrospective study</span></p> <p><span><b><span>Setting:</span></b> The Reproductive and Genetic Center of the Affiliated Hospital of Shandong University of Traditional Chinese Medicine, China.</span></p> <p><span><b><span>Participants: </span></b>1,061 pregnant women who underwent FET between January 2014 and January 2017.  </span></p> <p><span><b><span>Primary and secondary outcome measures: </span></b>Pregnancy outcome.</span></p> <p><span><b><span>Results: </span></b>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 &lt;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&lt;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 &lt;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&lt;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).</span></p> <p><span><b><span>Conclusion:</span></b> Serum β-hCG on the 7th day after FET has good clinical significance for the prediction of OP and AP.</span></p>