Use of the egg-share model to investigate the paternal influence on fertilization and embryo development after in vitro fertilization and intracytoplasmic sperm injection.

Objective: To investigate whether sperm from different males can influence fertilization and embryo development.

Design: To use an egg-sharing model, in which the eggs from one woman are shared between herself and a recipient, and different spermatozoa are used to fertilize the eggs.

Setting: Assisted Conception Unit, Birmingham Women's Hospital, Edgbaston, United Kingdom.