In some women with fertility problems, semen is placed manually during in
vitro fertilization procedures. Somehow, the semen has to get inside of the woman.
While it only takes one sperm to actually fertilize the egg, it takes millions of sperm to breakdown the corona (barrier) on the outside of the egg.
So, if there is no penetration and ejaculation, it is difficult to get enough sperm to the egg, for fertilization to occur.