Pregnancy outcome prediction after embryo transfer based on serum human chorionic gonadotrophin concentrations

The aim of the study was to evaluate the predictive value of the human chorionic gonadotropin (hCG) concentration on the 14th and 16th post-ovulation day after embryo transfer/cryoembryo transfer as well as the dynamics of its increase with respect to the outcome of pregnancy.

In total, 130 embryo transfers and cryoembryo transfers in women aged 22 to 38 years who experienced a single embryo transfer or single cryoembryo transfer with confirmed pregnancy (hCG level over 15 IU/l on 14th post-ovulation day - D14) were selected. The input parameters (hCG D14, hCG D16, hCG D16-D14, hCG D16/D14 and positivity of at least 2.5-fold increase in hCG D16 compared to hCG D14) were evaluated by regression analysis in relation to the outcome parameters (bio-chemical pregnancy, clinical pregnancy, clinical pregnancy terminated by abortion up to 12 weeks of gestation, clinical pregnancy terminated by childbirth).

Single concentrations of hCG D14 and D16, as well as the difference between these concentrations, were a statistically significant indicator of the prediction of bio-chemical pregnancy (P = 0.000215, P = 0.000227 and P = 0.000421). Contrary to expectations, the proportion of hCG D16 and D14 concentrations did not show statistical significance for either parameter, as well as the fulfilment of the condition of at least a 2.5fold increase in hCG D16 compared to D14. None of the studied input parameters was confirmed as a statistically significant marker for the prediction of miscarriage in the whole group of patients. However, in the group of confirmed clinical pregnancies, the serum concentration of hCG D16 (P = 0.0248) and the difference between concentrations D16 and D14 (P = 0.0185) were confirmed as a positive predictor of the progression of pregnancy until delivery.

Single hCG concentrations are a good prognostic factor for predicting the outcome of pregnancy, but the determination of the cut-off limit is limited by inter-laboratory deviation as well as by timing of blood collection for hCG determination on the exact post-ovulatory day. The results of individual studies are therefore difficult to use in clinical practice. The dynamics of hCG concentrations appear to be a more reliable predictor of pregnancy outcome. In our cohort, we confirmed the statistical significance of the difference in hCG concentration between the 16th and 14th post-ovulation day not only for the prediction of bio-chemical pregnancy, but also as a predictor of the progression of clinical pregnancy into childbirth. To determine the optimal values of this difference, it is necessary to evaluate a larger group of patients. Conversely, the statistical significance of the proportion of hCG concentrations between the 16th and 14th post-ovulation day was not  confirmed.