In this<unk> , sperm are incubated with several<unk>  eggs. After seven to twenty hours, the number of sperm penetrations per egg is measured. The<unk>  eggs have had the<unk>  pellucida, the outer membrane, removed—hence,<unk> -free. Having all eggs penetrated by multiple sperm is considered to be a positive sign for fertility. Results suggest that men whose sperm fail the<unk> <unk>  are a third as fertile than those whose sperm pass. Although medical professionals often present the procedure as unable to create a embryo, these claims are not technically correct. If the human sperm succeeds in penetrating the<unk>  egg, a hybrid embryo is indeed created, known as a<unk> . These embryos are typically destroyed before they divide into two cells; were they left alone to divide, they would still be unviable.
Hamster zona-free ovum test
Sperm–cervical mucus contact test
Postcoital test
Vaginal wet mount
Egg hatch assay
Poppy seed test
Triple smear
Karyotype