Purpose: To determine if the presence of a lower percentage of metaphase II eggs during oocyte retrieval leads to a lower fertilization rate of these metaphase II eggs since they may be more likely to be not quite fully mature, and to determine if transfer of embryos made from these eggs leads to lower pregnancy and implantation rates. Methods: Fertilization and pregnancy rates determined according to deciles of percent of metaphase II eggs beginning with < 30%. Results: Though there was no difference in fertilization rates when comparing those with < 60% metaphase II eggs vs ≥ 60%, there were significantly higher clinical and live delivered pregnancy rates and implantation rates when there were ≥ 60% of the eggs retrieved that were metaphase II. Conclusions: An inferior pregnancy outcome with a lower percentage of metaphase II eggs despite similar fertilization rates is consistent with the hypothesis that subtle full maturation defects may result in pregnancy failure despite embryo transfer.