BBC: Dutch IVF centre probes suspected sperm mix-up. December 27, 2016 by Garret Vreeland in Law, Health During fertilisation, sperm cells from one treatment couple may have ended up with the egg cells of 26 other couples. Therefore there's a chance that the egg cells have been fertilised by sperm other than that of the intended father.I don't even want to contemplate the complexities of this.