Predicting the pregnancy outcome: Uncovering the link between β-hCG, patient factors and live birth in IVF.

Objective: The objectives of the study were to correlate live birth rate with the initial level of β-hCG in all patients undergoing embryo transfer and develop a predictive model of live birth based on patients' and assisted reproductive technology (ART) characteristics.
Study Design: Single-center retrospective cohort study, including a total of 7587 positive first serum β-hCG from women who performed fresh and frozen embryo transfer. Twenty-one variables related to patient characteristics and treatment modalities were analyzed by step-wise univariate analysis followed by multivariate analysis. The study included women between 18 and 45 years with a positive (>20 IU/L) serum β-hCG between January 2011 and December 2020 while it excluded cycles from donation of gametes, PGT and >3 embryos transferred simultaneously.
Main Results and the Role of Chance: Among the positive serum β-hCG measurements 5085 (67.0 %) resulted in live births. β-hCG was higher in the live birth group (691 IU/L) compared to the failed pregnancies group (304 IU/L) (p500 IU/mL provided a positive predictive value for live birth of 85.3 % (95 %CI 84.0-86.4). Failed pregnancies were more common among older maternal and paternal age. Previous abortions were more common in the failed pregnancies group (25.0 %) compared to the live birth group (19.4 %). The most common indication to treatment was male infertility, accounting for a larger portion in the live birth group (41.7 %). At multivariate analysis, the factors independently associated with live birth were: first serum β-hCG (OR 1.35, 95 %CI 1.32-1.37), maternal age (OR 0.93, 95 %CI 0.91-0.95), previous abortions (OR 0.77, 95 % CI 0.68-0.88). The number of embryos transferred showed a positive correlation below a maternal age of 39 (<35 years old OR 1.60, CI 95 % 1.32-1.94; <39 years old OR 1.27 CI 95 % 1.09-1.47). The prediction model incorporating these four variables resulted in a sensitivity and specificity with an area under the ROC curve of 0.798.
Conclusion: The study confirms the importance of the first value of β-hCG and proposes a predictive model that takes into account maternal age, number of embryos transferred, and obstetric history, thereby aiding in couples' counseling and ultimately improve patients' care.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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