Peter Griffiths, London: Fertility clinics may be forced to cap the number of multiple births to one in 10 because of the dangers posed to mothers and babies, the fertility watchdog said on Wednesday.

The Human Fertility and Embryology Authority (HFEA) wants to reduce the chances of women having more than one baby after receiving IVF treatment.

A quarter of births after IVF in Britain result in twins or triplets, compared to 1 in 80 following natural conception, the watchdog said. HFEA Chairman Shirley Harrison said multiple births put mothers and babies at greater risk of death and serious illness.

"We know that multiple birth is the single biggest risk of IVF," she said in a statement. "It is our primary job as aregulator to make sure that IVF treatment is safe and appropriate."

The HFEA has launched a three-month public consultation over ways to reduce multiple births while still giving women a good chance of conceiving.Among the proposals are a maximum 10% twin rate for clinics and a move away from implanting more than one embryo in a woman during each IVF cycle.

The watchdog also wants to raise awareness of the dangers of multiple births. Twins are five times more likely to die in the first week of life than a single baby and four times more at risk of having cerebral palsy, the HFEA said.

Mothers of twins are more at risk from diabetes, heart disease and pre-eclampsia, a life-threatening condition that causes high blood pressure.

Liberal Democrat science spokesman Dr Evan Harris said the use of single embryos would reduce the chance of pregnancy for some women.

"Moving to single embryo transfer will prevent a number of multiple births -- however, it will mean that many women will now need extra cycles of NHS IVF in order to get pregnant," he said.

Fertility specialist Yacoub Khalaf, a consultant at Guy'sand St Thomas' NHS Foundation Trust in London, said singleembryo transfer was advised "where it is possible, andclinically appropriate to do so"."In the last year our overall pregnancy rate has risen andour multiple pregnancy rate has been reduced," he said.

"This is a result of our programme to extend the amount of time the embryo is incubated -- from three days to five --before being implanted."