Figures published by the UK's Office for National Statistics (ONS) show that the number of multiple births in England and Wales rose by 20 per cent over the 10 years between 1992 and 2002. It is thought that increases in the use and availability of fertility treatments, such as IVF, may, in part, explain the rise. It is known that some fertility treatments increase the likelihood of having a multiple pregnancy and birth.
Multiple births are associated with premature and low birth-weight babies and increase the risk of a baby's death before birth or early in life. Compared with a singleton birth, the risk of long-term disability is around five times higher for twins and 18 times higher for triplets.
The ONS figures show that the proportion of multiple births per 1000 pregnancies climbed from 12.5 in 1992 to 15 in 2002. The statistics also show that women who become pregnant in their late thirties or their forties are more likely than younger women to have a multiple birth. This is possibly because women in this age range may be more likely to use fertility treatments in order to conceive. The multiple birth rate in women aged between 35 and 39 was 21.9 pregnancies per 1000 in 2002, and for women aged between 40 and 44 it was 21.1 per 1000 pregnancies.
Last month, the Human Fertilisation and Embryology Authority (HFEA), the body charged with licensing and regulating the provision of fertility treatment in the UK, issued new guidelines to clinics limiting the number of embryos that can be transferred during treatment, in order to reduce the number of multiple births. The new guidance, which comes into force in March, stipulates that clinics should transfer no more than two eggs or IVF embryos at a time to women under 40 years old and no more than three eggs or embryos to women older than 40, with no exceptions.