Possibility of live birth in patients with low serum β-hCG 14days after blastocyst transfer

Background Although prior work has attempted to predict pregnancy outcomes by assaying serum beta-hCG levels after blastocyst transfer, no study has focused on pregnancy outcomes in those with initially low serum beta-hCG levels. This study sought to investigate pregnancy outcomes of patients with low serum beta-hCG levels 14days after blastocyst transfer. Methods A retrospective study was conducted at the Third Affiliated Hospital of Guangzhou Medical University to study patients whose serum beta-hCG levels were at 5-299 mIU/ml 14days 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 analysis. Receiver operating characteristic (ROC) curves were plotted to explore the threshold of predicting clinical pregnancy and live births. Results 312 patients had serum beta-hCG levels <300 mIU/ml at 14days after frozen blastocyst transfer, among which, 18.6% were live births, 47.4% were early miscarriages, 22.8% were biochemical pregnancies and 9.6% were ectopic pregnancies. ROC curve analysis showed that a predicted value of beta-hCG for clinical pregnancy was 58.8 mIU/ml with an area under the ROC curve (AUC) of 0.752, a sensitivity of 95.0% and specificity of 53.5%. The threshold for live births was 108.6 mIU/ml with an AUC of 0.649, a sensitivity of 93.1% and a specificity of 37.0%. For the beta-hCG fold increase over 48h, the cut-off for clinical pregnancy was 1.4 with an AUC of 0.899, a sensitivity of 90.3% and a specificity of 77.8%. The threshold for live birth was 1.9 with an AUC of 0.808, a sensitivity of 88.5% and specificity of 64.5%. Conclusions Initially low serum beta-hCG levels 14days after frozen blastocyst transfer indicated minimal chances of live birth. For patients having an initial beta-hCG >58.8 mIU/ml, luteal phase support should continue. Another serum beta-hCG test and ultrasound should be performed one week later. When an initial serum beta-hCG is <58.8 mIU/ml, luteal phase support should be discontinued and serum beta-hCG measured with ultrasound one week later.