In vitro fertilisation (IVF). Conceptual computer artwork showing an egg cell (ovum) in a test tube, with DNA in the background. IVF is a fertility treatment where an egg cell is fertilised by a sperm cell outside the body. Once embryos begins to develop, they are implanted into the womb. Before implantation, the embryos are genetically tested to ensure they are healthy, in a process known as pre-implantation genetic diagnosis. Some people fear this could lead to parents having the power to choose the characteristics of their baby.