Cytologic investigation of human in vitro fertilization failures

A cytogenetic study of unsuccessfully fertilized oocytes was done for information on the frequency and type of chromosomal abnormalities leading to preimplantation loss. Of 72 oocytes, 44 were assessed as mature, 19 as intermediate, and 9 as immature. The mean fertilization rate was 68%. This rate was significantly lower in immature oocytes than in mature ones (22% versus 79%). Immature oocytes completed maturation in vitro up to metaphase II of meiosis. Intermediate oocytes became fertilizable, however, a significant proportion showed morphologic abnormalities after fertilization. Thus, eggs with three pronuclei were hypotriploid or had three prophasic chromosome sets, together with polyspermy and with first polar body chromosomes. Eggs with developmental arrest showed marked asynchrony in pronuclear morphogenesis. One had a chromosome complement of 24,XX. It is concluded that insemination prior to completion of maturation leads to abnormal development.