Infertile couples who want more than one child should be encouraged to try for IVF twins in spite of the medical consensus that multiple pregnancies should be avoided, a senior American doctor said.

The health risks of conceiving twins by IVF have been exaggerated by the medical profession, and a British initiative to cut the number of such pregnancies is “categorically wrong”, according to Norbert Gleicher, of the Centre for Human Reproduction in New York.

He told the European Society of Human Reproduction and Embryology conference in Barcelona that for many women who need IVF to conceive, the birth of twins is a “favourable and ethical” result.

Such pregnancies provide complete families at a stroke, and may often be safer than having two singleton IVF pregnancies, he said. Moves to persuade more women to use one embryo at a time during fertility treatment, as recommended by a UK national strategy launched last week, are thus misguided.

Professor Gleicher's comments were fiercely disputed by other senior doctors, who said that his opinions were based on a flawed analysis of the risks of multiple pregnancies to both babies and mothers.

Professor Peter Braude, of King's College, London, said that IVF twin pregnancies are well-established to be more hazardous than singleton conceptions, with dangers that include prematurity, stillbirth, low birth weight, cerebral palsy, pre-eclampsia, haemorrhage and maternal death.

“Couples should be extra cautious about interpreting this advice because it flies in the face of all other published data about the risks of multiple births,” he said.

The conference executive, which is encouraging IVF clinics across Europe to move to single embryo transfer to guard against multiple births, said in a statement: “There are significant risks to multiple pregnancies, and we should not be generating them deliberately. IVF babies also deserve the best start in life.”

A Human Fertilisation and Embryology Authority (HFEA) expert panel, chaired by Professor Braude, found in 2006 that twins have five times the usual risk of death in the first year of life and six times the risk of cerebral palsy. More than half are born prematurely, and 40 to 60 per cent require intensive care. Each twin costs the NHS 16 times as much as a singleton birth in the first year of life, and it is estimated that 126 deaths would have been avoided had all IVF twins born in Britain in 2003 been singleton births.

Multiple pregnancies are also dangerous for mothers. A quarter are complicated by problems such as high blood pressure, and the death rate is doubled for women expecting twins.

These dangers have led the HFEA and the British Fertility Society to launch a national strategy to reduce Britain's IVF twin rate from 24 per cent to 10 per cent by 2012. This is likely to require single embryo transfer in about 50 per cent of IVF cycles, compared to about 10 per cent at present.

Professor Gleicher, however, claimed that some of these risks had been over-estimated, because they have been calculated by comparing twin births with just one singleton pregnancy, not two. “When you ask infertile patients having treatment, a very large majority want more than one child,” he said. “The question is how you get two children, not one. When you add the risks of two singleton pregnancies together, many risks of twins disappear.

“For infertile patients, desirous of more than one child, twin deliveries represent a favourable, cost-effective and ethical treatment outcome, which in contrast to medical consensus, should be encouraged.

“Because the alleged excessive risks and costs of twin deliveries have been the primary motivation behind the recently increasingly popular concept of single embryo transfer, the clinical, ethical and economic validity of single embryo transfer should be seriously questioned.”

He added that much of the medical literature is based on comparisons between naturally conceived singletons and twins. This may be misleading because IVF twins have a lower risk than spontaneous twins of dying at or soon after birth.

In a paper published in the journal Fertility and Sterility, Professor Gleicher has suggested that when these factors are taken into account, IVF twin pregnancies are less risky than two singleton conceptions for complications including stillbirth, neonatal death and major birth defects.

Professor Braude and the conference doctors pointed out that even Professor Gleicher's adjusted figures show substantially raised risks of maternal death, low birth weight and pre-eclampsia, a life-threatening blood pressure disorder.

They added that for many risks, it is statistically misleading to compare twin pregnancies with two singleton pregnancies. Professor Mark Hamilton, the chairman of the British Fertility Society, said: “It is misleading, as he has done, to combine the risks of two single live births which are two independent events, each with a lower risk than that of a twin pregnancy.

“With singleton pregnancies, the chance of having a stillborn baby, or one that dies soon after, is about five per 1,000. In a twin pregnancy it's four to five times that. If your first singleton pregnancy was uncomplicated, your chance of a problem the second time round is even lower, probably less than one in a thousand. Multiple pregnancies unquestionably expose mothers and babies to increased hazards.”

Professor Gleicher's study has also ignored the long-term health risks of the low birth weights suffered by twins, and the psychological impact of multiple births on parents.

A separate study presented at the conference, from Helsinki University Central Hospital in Finland, has found that the mothers and fathers of twins suffer significantly more mental health problems, such as depression, anxiety and sleep disorders, than the parents of singletons.

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