Several pregnancies are in progress in which cloned test-tube embryos were implanted in host mothers, but there have been miscarriages, according to the head of a human cloning firm run by the Raelian movement.
"Yes, we have viable pregnancies, that is to say three months or more," French scientist Brigitte Boisselier, president of the firm Clonaid, said from Clonaid headquarters in Las Vegas.
Implants of blastocysts, or embryos four to five days from conception, had begun in February and March, she said, but she did not give details on how many, the stages they were at, or the outcomes.
Miscarriages had occurred, she said, "as they do in test-tube conceptions."
Several specialists in the field, including biologist Rudolf Jaenisch of Massachusetts Institute of Technology's Whitehead Institute, say such experiments are not only doomed to failure, but are "irresponsible and repugnant."
Clonaid is owned by the Rael sect, which is led by former journalist Claude Vorilhon, a Frenchman now based in Quebec. Claiming to have 55,000 followers around the world, Raelians believe life on Earth was established by extraterrestrials who came here in flying saucers 25,000 years ago and cloned the human race.
Mr. Jaenisch and others have long spoken out against human cloning, a technique that has had a high failure rate in animals and resulted in "a veritable gallery of horrors" among aborted fetuses and live births.
They include, he said, congenital malformations, physical deformities, immune system deficiencies and premature aging.
Among the small number of cloned animals that live more than a few days, many suffer defects or disease including pneumonia, liver deficiency, obesity and premature aging, Mr. Jaenisch said.
However, Miss Boisselier said, examination of aborted cloned fetuses would have shown no abnormalities, implying the problem may have been in the birthing rather than the gestation.
Last July, at the first International Bio Exposition in Tokyo, Clonaid Vice President Thomas Kaenzig said the company was doing cloning in "10 to 20 clients," and that "50 host mothers" had agreed to undergo the implant procedure.
Other scientists also are in the race to produce the first cloned human.
Italian gynecologist Severino Antinori said in May that three women were pregnant with cloned embryos and that Russian and Chinese teams were engaged in similar experiments.