Prolongation of the Follicular Phase in in Vitro Fertilization Results in a Lower Ongoing Pregnancy Rate in Cycles Stimulated with Recombinant Follicle-stimulating Hormone and Gonadotropin-releasing Hormone Antagonists

Objective: To assess the effect of altering the timing of hCG administration on ongoing pregnancy rates in patients stimulated with recombinant FSH (rec-FSH) and GnRH antagonists for IVF.

Design: Prospective, randomized, controlled trial.

Setting: Tertiary referral center.

Patient(s): Four hundred thirteen patients undergoing IVF.

Intervention(s): Rec-FSH stimulation starting on day 2 of the cycle combined with daily GnRH antagonist starting on day 6 of stimulation. Patients were randomized to receive 10000 IU of hCG either as soon as at least three follicles were >or=17 mm on ultrasound (early-hCG group, 208 patients) or 2 days later after this criterion was met (late-hCG group, 205 patients).

Main Outcome Measure(s): Ongoing pregnancy rate.

Result(s): Fertilization rates and number and quality of embryos transferred did not differ between the two groups. However, a significantly lower ongoing pregnancy rate was present in the late-hCG as compared with the early-hCG group (25.0% vs. 35.6%, respectively).

Conclusion(s): Prolongation of the follicular phase in patients stimulated with rec-FSH and GnRH antagonists for IVF does not affect oocyte or embryo quality but is associated with a significantly lower ongoing pregnancy rate.