Fertilization, cleavage, and cytogenetics of 48-hour zona-intact and zona- free human unfertilized oocytes reinseminated with donor sperm

Abstract

Objective: To examine the fertilization rates of 48-hour unfertilized oocytes inseminated with fertile donor sperm and to evaluate the cleavage and cytogenetics of ensuing embryos. Design: Prospective. Setting: Assisted reproductive technology (ART) program. Patients: Four hundred ninety-seven unfertilized oocytes from 97 ART patients were categorized into four groups. A (zona-intact) and B (zona-free) were from patients with partial fertilization failure, whereas C (zona-intact) and D (zona-free) were total fertilization failures. Results: Fertilization rates in groups A and B were significantly higher than C and D (33.2% to 60.9% versus 20.0% to 48.1%; P < 0.01). Zona-free oocytes had higher fertilization rates than zona-intact oocytes (48.1% to 60.9% versus 20.0% to 32.2%). Multiple pronuclei were high in zona-free oocytes (33.1% to 41.3%). Forty-eight to 54% of embryos generated after donor insemination had chromosome anomalies (mosaicism, aneuploidy, pulverization). Conclusions: One cause of total fertilization failure appears to lie in intrinsic oocyte problems confined to the zona and oolemma. The fertilization of 48-hour unfertilized oocytes may be of some value in diagnosing fertilization failure in ART patients.