The definition of conception is a difficult one because this is not strictly a medical or scientific term. Some people believe conception to the be moment at which the egg is fertilised by a sperm, while others prefer to think of it as the moment that an early stage embryo implants in the lining of the uterus and becomes attached to its mother.
For most couples experiencing infertility, who may need fertility treatment to be able to have a child, conception is the ultimate goal and they tend to define it as ‘getting pregnant’. Although conception may be the start of pregnancy, the knowledge that a woman has conceived only comes with the positive pregnancy test that is possible 2–3 weeks after fertilisation, and a few days after implantation of the tiny embryo.
Defining conception in the context of fertility treatments is even more complex. During in vitro fertilisation, several eggs are mixed with sperm and are fertilised, but no pregnancy is yet in progress because the developing embryos are still in the laboratory in the fertility clinic. Some of the viable embryos may be frozen for a future cycle of frozen embryo transfer, so may not be transferred into the woman’s uterus for several years. Is it right to say that these embryos have been produced by conception, or does that only happen when they are transferred into the woman’s uterus, or when they implant into the uterine lining?
In surrogacy there are more questions about when and where conception occurs, and whether the woman donating the eggs has conceived, or whether this is only possible for the surrogate.
The intense discussions that continue to centre on the definition of conception have led the medical world to prefer the terms fertilisation and implantation to avoid unnecessary confusion. However, people who are very much against abortion argue that this distinction does not help, as it does not define when human life begins.