PREIMPLANTATION GENETIC TESTING: UNDIVINE INTERVENTION?

“Do we want to have a society where parents can flip through a DNA catalogue and design their own ‘boutique baby’? Will we accept that it is perfectly reasonable to discriminate against people before they are born, or prevent them from being born, because we don’t like their genes?” Dean Hamer, Geneticist at the National Cancer Institute from “Remaking Eden” by Dr. Lee M. Silver.

By: Dean E. Masserman, Esq.

Until recently, genetic disorders could only be detected during pregnancy using one of two methods: amniocentesis and chorionic villus sampling. Amniocentesis is done when the fetus is twelve to sixteen weeks old and consists of drawing a sample of the amniotic fluid from around the fetus and examining a floating cell from the fetus. Chorionic Villus sampling involves taking a small sample of the placenta at an early stage of development and examining it in the laboratory. The problem with these two procedures is that they can only be performed after conception, and after significant fetal development. Therefore, if the analysis shows that the fetus is genetically defective, the parents are faced with a decision of whether or not to terminate the pregnancy.

However, thanks to recent advances in genetics, an alternative procedure now exists which enables geneticists to diagnose most genetic defects in the embryonic stage, before pregnancy is established. This technique would vitiate the need for screening during the pregnancy and hence prevent the psychological trauma associated with terminating a pregnancy where genetic defects are detected. Moreover, it will enable couples who are carriers of profound genetic disorders to significantly decrease the risk of having a child that is afflicted with the same problems. For these couples, this technology is a miracle that will enable them to create a healthy family. To the majority though, the consequences of such intervention is daunting as it raises issues of sex selection and genetic engineering. Preimplantation Genetic Diagnosis (PGD), is a recently developed technique that can be utilized during In Vitro Fertilization (IVF) procedures to test embryos for various genetic disorders prior to an intrauterine transfer. PGD was made possible by the advent of a process called polymerase chain reaction (PCR) which allows a specific DNA sequence to be replicated many times and then rapidly analyzed.

The advent of PCR has been characterized as the most important scientific discovery of the twentieth century; completely changing the course of the biological and biomedical sciences. In the field of third party reproduction the effects of these advances are profound, and the procedures quite simple.

Embryos are obtained by combining an egg and a sperm in a petri dish under laboratory conditions. (IVF). As each embryo divides to about the 8 cell level it is isolated and a blastomere (single cell) is removed from each embryo and tested for the presence of genetic disorders; the entire process taking only 12-24 hours. Those that display some type of genetic abnormality are disposed of and the unaffected embryos are transferred back into the uterus in the IVF cycle. This highly sophisticated technique called micro- manipulation does not adversely affect further development of the embryo and has already produced more than thirty pregnancies worldwide. More importantly, it has been scientifically shown to effectively detect a wide variety of genetic diseases including cystic fibrosis, Tay-Sachs, Duchenne muscular dystrophy, hemophilia, fragile X-syndrome, retinitis pigmentosa, Lesch-Nyhan syndrome, Charcot Marie tooth disease, gender down syndrome, Marfan syndrome, spinal muscular atrophy (SMA), and could be employed to detect nearly 200 other gender related genetic disorders.

So where is the dilemma? PGD is simple, non-intrusive, relatively cost efficient and extraordinarily accurate. PGD avoids the stress and emotional trauma of having to terminate a pregnancy and enables couples to have a child with the full assurance that it will not be carrying any genetic disease passed on by them. Simply put, it allows parents to manipulate the process of natural selection and therein lies the rub. The dilemma facing geneticists, and soon the world at large, is whether or not such intervention is moral, and to what extent the practice should be utilized. The technology has much broader application than that discussed thus far. Prospective parents can not only screen for genetic defects, but potentially could determine the entire genetic makeup of the their unborn child. They may opt for a more artistic female child with fair skin and blonde hair. They may want a male child who is more analytical and has a passion for sports. Or, they may simply use PGD as a sex selection tool. And some couples may try to screen out the DNA alleles that account for obesity, high blood pressure and acne.

Additionally there are the fundamental religious considerations. Some might consider this procedure murder because the cell that is removed could have conceivably developed into a fetus, but instead it was destroyed as part of the testing. Others might contend that a genetically fertilized egg, if allowed to mature and result in a live birth, may not produce a defect at all, or may not manifest any symptoms until the person is in his/her early thirties or forties by which time a cure could be developed.

These illustrations, albeit extreme, do serve to make a point. PGD may take us down a road that will rapidly transform to a slippery slope. Currently, only a handful of specialized institutions with excellent IVF and molecular biology laboratories offer preimplantation diagnosis, and only to those couples at high risk, or those who have already had an affected child. However, with the coming of the new millennium, so comes a plethora of legal, ethical and moral quandaries that will literally shape our children and the world they live in.

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