Transgender

Forum













%expand(%include(D:\http/ads/ads0.html))


Two Embryos Form One Child

By Reuters
Contributed by Deeva Vincent

BOSTON
January 15, 1998


Medical researchers in Britain have found an unexpected risk in the implantation of more than one fertilized egg in the womb of a woman undergoing in vitro fertilization.

They have found a case in which two embryos, one male and one female, fused in development to form a single child.

The case, outlined in Thursday's New England Journal of Medicine, surfaced when an otherwise healthy child was treated because his left testicle had not descended normally. Surgeons discovered an ovary and a fallopian tube on the left side.

Otherwise the child, now in school, has developed normally.

In medical terms, the child is known as a chimera, named after the mythical Greek monster that was part lion, part goat and part serpent.

The researchers, led by Lisa Strain of the University of Edinburgh, said the standard practice of implanting more than one embryo during in vitro fertilization made it possible for the two embryos to fuse.

``The observation of chimerism after in vitro fertilization should therefore be taken seriously,'' they said. Such phenomena can happen naturally, but it is very rare, so rare as to ''suggest a causal link to the in vitro fertilization,'' they said.

There may be more cases of chimerism than people realize, the Strain team speculated, because fusions between two male embryos or two female embryos would probably be missed since the baby would show no sex organ abnormalities.

The risk of chimerism has risen in recent years because more women are taking fertility drugs, which release multiple eggs for fertilization. Couples are also using in vitro fertilization, in which doctors routinely implant more than one fertilized egg to increase the likelihood that at least one will develop into a viable fetus.

The higher rate of multiple births after the use of fertility drugs or in vitro fertilization also means that more chimeric children may be found. In the United States and Canada, fertility drugs and in vitro fertilization techniques produce twins 28 percent of the time and triplets 6 percent of the time. The normal rates are 1 percent and 0.013 percent



Back to
TGF's
Home Page