Where do the embryos come from?

Where do the embryos come from?

There are currently at least 100,000 'spare' human embryos stored in freezers across the European Union.

These embryos were created as a routine part of infertility treatment (IVF). A single round of IVF treatment usually involves fertilising many eggs at the same time. Several fertilised eggs are then re-implanted into the mother, and the rest are frozen in case the first attempt to achieve pregnancy doesn't work.

If the IVF couple gets pregnant immediately, they may choose not to use their remaining embryos. In some countries couples have the option of either donating unwanted embryos for research or discarding them.

For some stored embryos, however, decisions about their fate were never made. Over the past 20 years since IVF began, many of the egg and sperm donors have changed their address, got re-married and changed their name or perhaps even died. Fertility clinics may be unable to trace them. The fate of many stored embryos is thus uncertain.

A second and even more controversial source of embryos to provide stem cells would be embryos created purely for research or treatment. There has never been any intention of implanting them into a woman. Creating an embryo for this purpose is considered by many people (and some governments) to be ethically wrong.

Nevertheless, there are millions of sperm and thousands of unfertilised eggs already in freezers in IVF clinics across Europe. If the sperm were used to fertilise the eggs, there would be even more embryos to supply stem cells to cure disease.

There is one final way of obtaining human embryos - using the cloning technique. This involves making a human embryo that contains the entire genetic make-up of someone who is already alive. If implanted into a woman's womb, the embryo could theoretically grow into a clone (a genetically identical copy) of that person. If used in research, the embryo could provide stem cells to cure disease.