Predicting Sex

It is normal enough for prospective parents to wonder about the sex of their unborn child. When their doctor shares their curiosity, though, he may well fear the presence of some sex-linked hereditary disease such as hemophilia, or certain disorders accompanied by mental retardation.

But even if today's doctor knew which sex to expect, and even if he could predict trouble, there would be little for him to do except prepare to interrupt the pregnancy or to provide treatment after birth. Soon, however, prenatal care for fetuses still in the womb may be possible for a host of problems. And if sex is an element in the diagnosis, the doctor will be more curious than ever. But how will he tell?

Last week three researchers at the Albany Medical Center offered a surprisingly accurate answer. And, oddly, that answer was developed as a byproduct of one of the few forms of therapy that can now be started while a baby is still in the womb. When incompatibility of the Rh blood factor between mother and child is serious enough, even a massive transfusion of blood immediately after birth is sometimes too late to save the child. And for such cases doctors have worked out a delicate technique for transfusion in utero. Before they try such major treatment, however, they insert a needle through the mother's abdomen to extract a sample of the amniotic fluid in which the fetus is floating. That sample may help to determine the severity of the Rh problem.

From that same sample, the Albany researchers have also learned to determine an unborn infant's sex. Micro scopic examination of carefully cultivated slides, they discovered, reveals the presence or absense of the sex-chromatin body that determines femininity. And in every case in which the sample was adequate, not only did all the researchers agree on their prediction, but in every case they were correct. Enthusiastically they reported that there is no reason why the test should not always be 100% accurate. Then they quickly added a word of caution. Since obtaining a sample of the amniotic fluid "is not without danger," they carefully noted that the new method should not be used simply "for satisfying the curiosity of the parents."

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