Objective: To investigate the effect of earlier administration of hCG according to serum concentrations of P on the outcome of IVF-ET in cycles in which a subtle rise in serum P (1.0 to 2.0 ng/mL; conversion factor to SI unit, 3.180) occurred during the follicular phase. Design: Retrospective study. Patients: A total of 110 infertile women underwent 124 cycles of IVF-ET at Tottori University Hospital. Main Outcome Measures: Serum was obtained daily or every 12 hours from day 7 until the administration of hCG. Serum E(2) and P concentrations were measured by RIA. In 19 of 36 subtle P rise cycles, hCG injection was given when the levels of serum P exceeded 1.0 ng/mL (''rescued'' subtle P rise). Parameters of NF outcomes for the no P rise, the subtle P rise, and the rescued subtle P rise cycles were compared. Results: The mean day of hCG administration in the rescued cycles was 1 day earlier than those of the subtle P rise and no P rise cycles. The mean number of oocytes collected was significantly higher in the subtle P rise and rescued P rise cycles than in the no P rise cycles. The mean follicular diameter on the day of hCG administration was 13.9 mm in the rescued cycles, significantly smaller than those of the no P rise and subtle P rise cycles. However, there was no significant difference in the cleavage rates between the three groups. The rate of embryonic development beyond four-cell stage was increased significantly in the rescued cycles and no P rise cycles versus the subtle P rise cycles. Embryos obtained in the no P rise and rescued cycles were of better morphological quality than those obtained in the P rise cycles. The implantation rate was significantly higher in the rescued cycles than in the P rise cycles. Conclusion: The data suggest that, if hCG is administered when a subtle P rise is detected, embryo quality and subsequent implantation rate can be improved.
