The tighter controls come after an "epidemic" of test tube babies born with birth defects including cerebral palsy and spina bifida.
The authority, which advises the Government, has been repeatedly asked by doctors to ban women from being implanted with more than two fertilised test-tube embryos, because multiple births have been linked to a rising tide of problems. A formal recommendation to the Government is expected in the New Year, a step which will almost certainly result in legislation.
Half the triplets born in the UK are as a result of IVF treatment, now a routine way of conceiving given the high rates of fertility problems in the UK.
However, fertility specialists have told the HFEA that the social and financial cost of multiple births and of treating test- tube babies born with disabling illness is too great. They have been urging it to ban implants of three embryos, which account for 60 per cent of procedures.
The authority, which regulates NHS and private test-tube baby clinics, agrees that multiple births are a cause for concern for mothers and babies and, officially, says it is keeping a watching brief.
Prof Allan Templeton, professor of obstetrics and gynaecology at Aberdeen Maternity Hospital and a member of the HFEA, says only the "best" one or two embryos should be implanted. He says evidence from his own work shows that the chances of a successful birth are as good when two embryos are implanted as they are when three are used.