Down’s syndrome is a genetic condition involving an extra chromosome, this change occurs around the time of conception. A person with Down’s syndrome has forty-seven chromosomes instead of the usual forty-six. A relatively common genetic disorder, Down’s strikes 1 out of 600 babies. In 95 percent of all cases, the disorder originates with the egg, not the sperm, and the only known risk factor is advanced maternal age-at age 35, a woman has 1 chance in 117 of having a baby with Down’s; at 40, her odds are 1 in 34. (Graves, 1990)
People with Down’s syndrome all have a certain degree of learning disability . This means that they develop and learn more slowly than other children. However, most children with Down’s syndrome today will walk and talk, many will read and write, go to ordinary school, and look forward to a semi- independent adult life. (Platt and Carlson, 1992) Facts on Down Syndrome *Down syndrome is not a lethal anomaly. One to two percent of persons born with this disorder have uncorrectable heart defects at birth. The average life expectancy for all others is now beyond age 55 years. Today less than 5% of persons with Down syndrome have severe-to- profound mental retardation.
The majority are on the border of mild-to-moderate mental retardation, and some are exhibiting normal IQ scores today. *The average reading level for persons with Down syndrome is 3rd grade, with many reading at 6th-12th grade levels today. *The vast majority of adults with Down syndrome today can be expected to live semi- or totally independently and many enter the work force with today’s supported employment programs and some are competitively employed.
Scientists at Norfolk’s Jones Institute for Reproductive Medicine say they have overcome most technical hurdles to screening embryos for Down syndrome and many other chromosomal defects before the embryos are implanted in a woman’s uterus. The institute, part of Eastern Virginia Medical School, hopes to try out the technique with a handful of high-risk couples who come to the institute for in-vitro fertilization, in the near future.
Eventually, all couples who go through the Jones Institute may have the option to screen for Down and most of the other conditions caused by an extra hromosome on one of 23 pairs that make up the normal complement. The technique has been developed in part to help parents avoid a difficult moral decision – what to do if the fertility techniques cause the mother to become pregnant with many children at once. At the same time, it opens up a host of other ethical questions for parents and society as a whole, say people who have children with Down.
According to Kingsley and Levitz (1994), in-vitro fertilization (IVF), is a technique in which eggs are removed from a woman’s ovaries and combined ith sperm in a dish. The resulting embryos are transplanted into the woman’s uterus. Before transplant, a single cell will be removed and exposed to probes made up of genetic material treated with fluorescent dye. Each probe has been designed to attach to a specific chromosome in the nucleus. Using a special microscope, a scientist can count the dots of various colors. Three of a specific color means that there is one extra chromosome of that type.
The institute will test five pairs that account for most chromosomal defects. The first cases will be done for free. When the procedure becomes common, the procedure will add about $2,000 to the cost of IVF, about $7,500. The Chairman of reproductive endocrinology at the Jones Institute said the procedure was developed primarily to avoid the multiple births that sometimes happen with IVF. (www #1) Most transplanted embryos, and many naturally conceived ones, never take root and grow because they have the wrong number of chromosomes.
In IVF, doctors try to improve the odds by implanting three or more, assuming that some will be lost. But sometimes, many or all of the embryos are viable. The parents then must decide – do they selectively abort some, or do they take on the hugely demanding task of having many babies at once? If doctors could screen the embryos, he said, they could limit themselves to implanting two and still enjoy a high probability that the embryos will survive. Nevertheless, the ability to screen out embryos with Down syndrome still worries families of people with the condition.
The option not to have a child with Down already exists. Tests during pregnancy can detect the condition. Parents may choose an abortion. Parents of hildren with Down syndrome, say that other parents who choose to discard an embryo in a laboratory are further removed from the implications of their decision. Doctors at the medical center say that they want very much for people confronting the decision to understand that having a child with Down syndrome can be very fulfilling.
They says the Jones Institute isn’t trying to devalue people with Down syndrome by offering the test. But they say this information has such important ramifications for the family, if we have that information, we would give it to them and they make the choice. Polar Body Analysis Physicians at Illinois Masonic Medical center have discovered that they can determine if a woman will have a baby with Down’s syndrome before she gets pregnant, provided she is willing to undergo in-vitro fertilization.
Using an experimental technique called polar body analysis, the genetic material of an egg can be checked before laboratory fertilization, helping some women avoid abortions. Chicago researchers at Masonic reported on a yearlong study involving 100 women who underwent the polar body procedure, they say that several women lready have delivered healthy babies, and more than 20 are pregnant with no sign of Down’s. But the possibility exists that the Masonic patients could have achieved the same results without genetic testing.
The majority of women who have conventional in-vitro fertilization are older and have normal pregnancies. Dr. Charles Strom, director of medical genetics at the hospital said that, polar body work gives a 35-year-old female the same chance of conceiving a chromosomally normal baby that a 21-year-old has. He said at least half the women in the in-vitro fertilization program are 35 or older. www #2) Polar body analysis hinges on basic biology. During normal development, the human egg contains a sac of excess chromosomes called the polar body before it gets ready to be fertilized by a male’s sperm.
Since this sac, is a mirror image of the egg, the genetic content of the egg itself can be determined through this procedure. (www #3) Without such testing, about 30 percent of the Down’s pregnancies resulting from in-vitro fertilization would have miscarried naturally, and others could have been picked up by the standard prenatal testing techniques, chorionic villi sampling and amniocentesis. In-vitro fertilization is expensive, labor intensive and often disappointing.
The polar body test would add another $2,000 to $2,500 to its costs. www #2) The Triple Screen The “triple screen for Down syndrome” has been in existence for over five years. However, just this past year, the American College of Obstetricians and Gynecologists officially recommended that this test be offered to all pregnant patients of all ages. This implies a legal mandate to practicing physicians who cannot afford the liability of not offering such a test after a national recommendation has been made. This “mandate” has been met with great controversy.
The “triple screen” actually involves drawing maternal blood to test for serum levels of three hormones: human chorionic gonadotropin (HCG), alphafetoprotein (AFP), and estriol (E3). The pattern of the levels of these hormones predicts the presence of Down syndrome in the fetuses in up to 60-70% of pregnancies affected. By using computer formulas, the hormonal levels can be found that are predictive for a risk of Down syndrome in the fetus that approximates 1 in 190 – which is the same risk that a pregnant woman has at age 5.
Thus, the test has been recommended now for women at all ages. If it is “positive”, it should be followed by ultrasonography and then amniocentesis to make a definitive diagnosis. (www #3) Some uses of the triple screen are seen as positive by all. If the test is negative, these results can prevent further unnecessary ultrasonography, or amniocentesis, or chorionic villus sampling – for women 35 or over; or for the woman with a previous fetus with Down syndrome. Normally these more expensive and invasive tests would have been recommended in those settings.
It is the use of the test for all pregnant women that begins to stir controversy. Only one such serum test has ever been recommended so widely before – the serum (AFP) alphafetoprotein screen. It is a screening test for multiple types of fetal defects that affect the “neural tube” in the fetus. These defects include such problems as anencephaly, holoprosencephaly, or einencephaly, as well as many levels of spina bifida. Down syndrome is certainly not the same as the wide range of anomalies termed “neural tube defects,” but the Triple Screen makes it seem an equal to many lethal defects.
The triple screen actually detects many more fetal anomalies than Down syndrome, including the AFP-related anomalies mentioned above and several lethal trisomies, such as Trisomy 18. The Triple Screen is called a screen “for Down syndrome” for marketing reasons, as much as for scientific accuracy. The Triple Screen is, in fact, a very poor screen, identifying only about 65% of fetuses with Down syndrome in utero. No other screen with such low validity has been universally recommended for all pregnant women. Such a recommendation means billions of dollars for the genetics industry and the researchers involved. (www #3)