The rate at which serum total beta-subunit human chorionic gonadotropin increases after embryo transfer is a predictor of the viability of pregnancy and an identifier of determinants of pregnancy.

Objective: To determine whether elements of treatment associated with faster doubling times of total beta-hCG in serum (beta-t2) in pregnant patients are also associated with a higher likelihood of pregnancy in all patients.

Design: Retrospective analysis of beta-t2 values, elements of ovarian stimulation (COH), and outcomes.

Setting: Private assisted reproductive technology (ART) center.

Patient(s): Initial analysis of data from 432 cycles in which conception occurred after COH and embryo transfer, followed by analysis of pregnancy outcomes after 1,287 cycles of COH/ embryo transfer.

Intervention(s): No interventions.

Main Outcome Measures: The beta-t2 values initially computed from consecutive serum beta-hCG levels in ongoing pregnancies were correlated with multiple properties of the patients and their treatment cycles.

Result(s): The beta-t2 values during early pregnancy increased exponentially from about 1.6 days at 12 days to about 3.0 days at 24 days after embryo transfer. In those pregnancies which spontaneously aborted, early average beta-t2 values were higher than those for ongoing pregnancies; absolute beta-hCG levels did not differ. Positive correlations were established between beta-t2 values, the number of days of stimulation, and the number of ampules of drug administered per oocyte retrieved. The beta-t2 values were inversely related to average numbers of blastomeres in transferred embryos. Ongoing pregnancy rates (PR) were higher for cycles with lower gonadotropin dosages per oocyte retrieved, and when the average number of blastomeres in transferred embryos was higher.

Conclusion(s): Steeper beta-hCG doubling times in early pregnancy were associated with lower gonadotropin dosages during ovarian stimulation and with higher numbers of blastomeres in transferred embryos. The latter variables were, in turn, associated with a higher likelihood of pregnancy after embryo transfer.