Background: Although many previous study investigated the prediction of pregnancy outcomes by serumβ-hCG levels after blastocyst transfer, no study focused on the pregnancy outcomes of patients with initially low serum β-hCG levels. The purpose of the study was to investigate the pregnancy outcomes of patients with low serum β- level 14 days after blastocyst transfer.
Methods: A retrospective study was performed in the Third Affiliated Hospital of Guangzhou Medical University. The purpose was to investigate the patients whose serum β-hCG levels were between 5-299 mIU/ml 14 days after frozen blastocyst transfer. Rates of live birth, early miscarriage, biochemical pregnancy loss and ectopic pregnancy were analyzed according to the female patients’ age by chi-squared test. Receiver operating characteristic (ROC) curves were plotted to explore the threshold for prediction of clinical pregnancy and live birth.
Results: A total of 312 patients had serum β-hCG levels <300 mIU/ml 14 days after frozen blastocyst transfer, among which 18.6% were live birth, 47.4% were early miscarriage, 22.8% were biochemical pregnancy and 9.6% were ectopic pregnancy. Pregnancy outcomes were comparable between the patients aged <38 years and ≥38 years. ROC curve analysis showed that the predicted value ofβ-hCG for clinical pregnancy was 58.8 mIU/ml with the AUC of 0.752(95%CI :0.680-0.823), sensitivity of 95.0% and specificity of 53.5%.The threshold for live birth was 108.6mIU/ml with the area under the ROC curve (AUC) of 0.649(95%CI:0.0.583-0.715), sensitivity of 93.1% and specificity of 37.0%.For the β-hCG fold increase over 48 hours, the cut-off for clinical pregnancy was 1.4 with the AUC of 0.899(95%CI :0.801-0.996), sensitivity of 90.3% and specificity of 77.8%; the threshold for live birth was 1.9 with the AUC of 0.808(95%CI :0.724-0.891), sensitivity of 88.5% and specificity of 64.5%.
Conclusions: Initially low serum β-hCG level 14 days after frozen blastocyst transfer indicated minimal likelihood of live birth. For patients having initial β-hCG >58.8 mIU/ml, luteal phase support is suggested to continue. Another serum β-hCG test and ultrasound should be performed one week later. If the initial serum β-hCG is < 58.8 mIU/ml, luteal phase support is suggested to discontinue and measurement of serum β-hCG and ultrasound can be arranged one week later.