This maximises the chances of at least one of the embryos resulting in a successful pregnancy. But proposals - from the Human Fertilisation and Embryology Authority - aim to limit women to one embryo wherever possible.
The regulator says this will cut the number of multiple births and reduce the health complications associated with them. One in four IVF babies is a twin or triplet. They are more likely to die before or during birth or to be premature, underweight or disabled.
It is estimated that if all IVF children were single births, 126 fewer babies would die each year. (Daily Mail)