[Paleopsych] NYT: Screening for Abnormal Embryos Offers Couples Hope After Heartbreak
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Tue Nov 22 16:50:47 UTC 2005
Screening for Abnormal Embryos Offers Couples Hope After Heartbreak
[Will we slide all the way down the slippery slope to utopia? Not if even
post-humans inherit the "abiding infirmities of the human race" that Mr.
Mencken so often spoke of.]
By LAURIE TARKAN
After enduring six miscarriages and undergoing six artificial
inseminations and two in vitro fertilizations, Kelly Santos, at the
age of 35, was dealt the final blow.
"My doctor told me that I would never have a biological child," said
Ms. Santos, who lives in Gillette, N.J. The diagnosis was a
chromosomal translocation, a mix-up in the arrangement of a few
genetic pieces that leads to a high proportion of abnormal embryos and
a 90 percent rate of miscarriage.
"It was depressing having all those miscarriages, but when they told
me it was over, I wanted to kill myself," she said.
By chance, she heard about a procedure called preimplantation genetic
diagnosis, a test that can screen out the abnormal embryos that cause
miscarriages. A year later, using the technique, she gave birth to a
healthy girl, Olivia.
Preimplantation genetic diagnosis, referred to as P.G.D., is an
increasingly popular way to ensure a healthy pregnancy for women who
have had multiple miscarriages, those having I.V.F. treatment and
couples that are carriers of a genetic disorder.
Only healthy, disease-free embryos are implanted into the uterus,
increasing the odds of having a successful pregnancy and a healthy
The test is no guarantee that a miscarriage can be avoided because
many factors can interrupt the normal course of a pregnancy.
P.G.D. has also been used by parents who want to have a child who is a
tissue match for a sibling with a devastating disease. These so-called
save-your-siblings can provide umbilical cord cells to the other
child, in some cases saving the sibling's life.
And a study published in Nature's online edition last month reported
that P.G.D. is also being used to develop embryonic stem cell lines
without destroying the embryo.
Amid the excitement, some experts urge caution, because of a lack of
research on the procedure's success rate, error rate and potential
Ethicists worry about a procedure that can also allow couples to
choose the sex of their child and may one day be used to select
embryos for traits like intelligence and physical strength.
There are some failures, and they can be devastating. Doreen Flynn,
29, of Lewiston, Me., had one daughter with Fanconi anemia, a disease
that leads to bone marrow failure and a high risk of leukemia and
other cancers at a young age.
Ms. Flynn and her husband had P.G.D. to create a tissue-matched baby
to provide cells to save their daughter.
Ms. Flynn said she had two tissue-matched embryos transferred, both of
which she expected to be disease-free based on medical information she
had received. She opted out of the amniocentesis because of the small
risk of miscarriage.
Two months after the babies were born, they were tested for Fanconi
and both girls had the disease.
"You feel so guilty because you're trying to help one daughter and you
end up hurting two other children," Ms. Flynn said. "Now we understand
that it's not an exact science and there's room for error."
Still, those who have been helped by P.G.D. describe it as nothing
short of miraculous. According to a 2004 survey by the Genetics and
Public Policy Center at Johns Hopkins University, about two-thirds of
the respondents approved of the use of P.G.D. to prevent a fatal
childhood disease and for tissue matching to save a sibling, said
Kathy Hudson, the center's director.
The procedure was first successfully performed in humans in 1989 in
London, after years of animal testing. It is currently performed in
about 10 percent of I.V.F. procedures annually in the United States.
(Some 100,000 I.V.F. cycles were performed as of 2002, the most recent
year to have complete statistics.) The test adds an estimated $2,000
or more to the already high cost of in vitro fertilization, which can
range from $7,000 to $10,000 for each attempt. A majority of women
turning to P.G.D. are those who have had more than three miscarriages
due to a translocation. Second on the list are I.V.F. patients who are
over 35 and have a high risk of having offspring with chromosomal
abnormalities, like Down syndrome.
Without P.G.D., many women over 35 get an amniocentesis around the
15th week of pregnancy to test for disabling genetic diseases. If a
disease is found, the couple then faces the choice of having an
abortion or bearing the child.
Andrew R. LaBarbera, scientific director of the American Society of
Reproductive Medicine, said, "That's very distasteful for many people
who don't have a problem undergoing P.G.D. to avoid this situation."
Also using the procedure are couples who are carriers of single-gene
disorders like cystic fibrosis, fragile X and Tay-Sachs disease. These
couples have an extremely high risk of passing the disease on to their
children and may have already given birth to a child with the disease.
Tests can be given for more than 100 single-gene disorders.
P.G.D. is performed when an embryo has only six to eight cells, called
blastomeres. The zona pellicuda, the outer shell of the embryo, is
opened with a micro needle, and a single blastomere is removed by
gentle suction and sent to a P.G.D. lab for analysis.
This does not kill the embryo because at this stage, each blastomere
is capable of developing into a complete organism, or totipotent.
It is not until the embryo passes the 16-cell stage that it begins to
differentiate and give rise to stem cells. Yuri Verlinsky, director of
Reproductive Genetics Institute, a leading P.G.D. lab based in
Chicago, projects that in the next couple of years, P.G.D. "is going
to be done for every I.V.F. case, because it definitely improves
But Dr. Hudson said there was not enough data on the risks and
benefits of P.G.D. and on the long-term health risks to the child.
Numbers coming out of the leading labs show that P.G.D. leads to
sharply lower rates of miscarriage and abnormalities, but the data
have been reported in different forms by the labs themselves, not by
Santiago Munne, director of Reprogenetics in West Orange, N.J.,
another leading center, published his miscarriage rates in the August
issue of the journal Fertility and Sterility. He reported doing the
test for 58 women with recurrent miscarriages.
They had experienced an average of 3.9 previous pregnancies, of which
87 percent were lost. After P.G.D., the miscarriage rate was only 16.7
At Reproductive Genetics, Dr. Verlinsky reported that of the 4,000
P.G.D. tests his lab has performed, there were 900 pregnancies and 700
Some experts are concerned about the rate of misdiagnosis.
There is a phenomenon called mosaicism, which occurs when the eight
cells that make up the early embryo are not identical.
Mosaicism occurs in about 30 percent of embryos. So a biopsied cell
could be abnormal while neighboring cells are normal.
During growth, the normal cells could dominate, producing a completely
healthy embryo. But with P.G.D., those embryos would likely be
On the other hand, if the biopsied cell is normal but the other cells
are abnormal, the result may be a diseased embryo.
"About 4 percent of P.G.D. will be misdiagnosed because of mosaicism
and maybe 1 percent more are misdiagnosed due to technical error,"
said Dr. Munne, drawing from his own data on chromosomal
abnormalities. Most of these abnormal embryos, though, will not
implant or survive, he said.
Dr. Munne said his own rate of clinical error, when a defective embryo
does implant and thrive, is 6 in 5,000 cases.
Of these six, all but one spontaneously miscarried; the other
pregnancy was terminated.
Dr. Verlinsky reported rates of error for single-gene testing. Of 250
babies, 5 were misdiagnosed; 2 were missed because of technical errors
and 3 were because of human error - transferring the wrong embryos.
But error rates vary among centers, and Dr. Munne recommends asking
for these figures before getting P.G.D.
Some experts worry that couples may not appreciate the risks. In one
survey, Dr. Hudson interviewed P.G.D. patients to see if they
understood the potential risks. "We got the impression that while the
information had been transmitted, it was not received," she said.
Many couples having P.G.D. see the procedure as foolproof and choose
not to have amniocentesis once pregnant because of the small risk
involved, said Dr. Serena H. Chen, director of the division of
reproductive endocrine and infertility at St. Barnabas Medical Center
in Livingston, N.J.
There are other ethical questions about creating one child to save
another. The most pressing, Dr. LaBarbera said, is what happens when
the cord blood transplant does not work and the parents decide to put
the child through a bone marrow transplant?
"That's a very painful procedure, but when you ask parents, they will
do anything to save a child they have," Dr. LaBarbera said.
There is no solid research on long-term effects on P.G.D. children,
but the potential risk of the procedure should be weighed against the
reason a family is getting it, Dr. Hudson said.
"In the case of a family who's facing a one in four or a one in two
chance of having a child with a fatal genetic disease," she said, "the
context is quite different from those who want to pick the sex of a
kid," she said.
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