In vitro fertilized human eggs. An electron microscopic study

This paper describes by scanning and transmission electron microscopy the u ltrastructure of the human fertilized egg and its vestments (cumulus oophor us and zona pellucida). Data are reported on the ultrastructure of a. conve ntional in vitro fertilized eggs (pronuclear eggs and cleaving eggs at two- to-four cell stage); b. eggs at the same developmental stage deriving fro i ntracytoplasmic sperm injection. The present results showed that: 1. The cu mulus-enclosed fertilized egg is a highly dynamic structure in which egg ve stments play a crucial role, positively affecting fertilization and healthy embryo development; 2. Intracytoplasmic sperm injection technique does not seem to significantly alter fertilized egg morphology.