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Whether a whole chromosome or a single gene or a group of genes is responsible, genetic defects can affect every part of the human body and the mind. Dr. Victor McKusick of Johns Hopkins, the world's leading expert on dwarfism, supplied a forbidding list: abnormalities of the skeleton, of the innumerable enzyme systems, of the nervous system, of blood cells, both red and white, of clotting mechanisms, of the hormone systems, of the kidneys, of the intestinal tract, and of the muscles. The eyes and ears are also susceptible—there are about 40 varieties of hereditary deafness, said McKusick —and so is the skin.
For the present, the international assembly offered more hope for prevention and improved treatment than cure of birth defects. One preventive technique is amniocentesis—inserting a needle through the pregnant woman's abdomen, into the amniotic sac, and withdrawing fluid for analysis of the cells shed by the embryo. For the apparently normal woman this would never be recommended. But it is a boon for the woman with a history of pregnancy mishaps, or one whose family is known to harbor inheritable defects. At Children's Memorial Hospital in Chicago, Dr. Henry L. Nadler reported, his department has "managed" 150 pregnancies on the basis of such cell studies. In 14 cases, abortion was recommended, and in 13 cases the abortion was carried out. In the 14th, the mother of one mongoloid child said she would rather have another mongol than an abortion—and she did. In the other 136 cases, no abortion was recommended, and all the babies born were normal. This procedure, Nadler emphasized, neither encourages abortions nor increases their incidence. What it does is enable couples capable of transmitting genetic defects who desperately want normal children to have almost the same chance of having them as couples with no such problems.
Risks of Age. More and more defects, especially those resulting from lack of an enzyme, are now being detected. In most cases, the only "remedy" is abortion. But sometimes it may be possible to contain an enzyme deficiency by altering the mother's diet. If the embryo is developing unnaturally because of faulty nutrition, it even may be possible to inject nutrients into the amniotic fluid, which the fetus absorbs.
A factor over which would-be parents have some control, provided they start to exercise it early enough, is the age of the ovum at the time of conception. Rockefeller University's Dr. E. Witschi reported that studies in several animal species show that an old or "stale" egg is especially likely, if fertilized, to result in the birth of a defective baby. In humans, it is known that the risk of having a mongoloid, for instance, increases from one in 2,000 births for a woman at age 25 to one in 50 at age 45. For a woman's ova, unlike her husband's sperm, are not manufactured continuously so that they are always fresh, but are laid down in a sort of pre-egg form while she is still in her mother's womb, or shortly after birth. This explains why the mother's health, at conception and during pregnancy, may be important a generation later. Therefore, West Germany's Dr. Widukind Lenz concluded, "the present trend toward earlier sexual maturity, earlier marriage and earlier reproduction is biologically favorable."