Thursday, September 21, 2006

More and more couples are turning to an embryo-screening technique that allows them to choose the genetic makeup of their children, according to a survey released yesterday in the online edition of the journal Fertility and Sterility.

Some use the test so they can give birth to a child genetically similar to a sick sibling in need of a bone marrow transplant from a matched donor. Others are screening for genetic abnormalities, including some for which the test has not been proved useful. Still others are using it to get a baby of the sex they want.

Pre-implantation genetic diagnosis, or PGD, starts with the creation of a "test tube" embryo. At the eight-cell stage of development, one cell is removed, apparently without causing lasting harm, for testing. Embryos that pass the test are allowed to develop further and are transferred to a woman's womb. Others are frozen or discarded.

The survey of 186 U.S. fertility clinics, conducted by the Washington-based Genetics and Public Policy Center, found:

· About 75 percent of fertility clinics now offer PGD.

· About 3,000 PGD screenings were performed in 2005 -- in 5 percent of all in vitro fertilization procedures.

· Sixty-six percent were done to screen out embryos with chromosomal abnormalities that were feared because the mother was older or had a history of in vitro fertilization failure or miscarriage caused by chromosome problems -- even though PGD has not been deemed a reliable test for these problems.

· Forty-two percent of clinics doing PGD offer sex selection, and 9 percent of PGD is for this purpose.

· Twenty-four percent of clinics offer PGD to get a match for a sibling in need of a transplant, about 1 percent of all PGD.

· Twenty-one percent of PGD clinics were "aware of" errors having been made -- including children born with the problem that was supposed to have been screened out.

-- Rick Weiss