February 10, 1969

Dr. J. A. Fraser-Roberts

Pediatric Research Unit

Guys Hospital Medical School London,

Dr. J. A. Fraser-Roberts

Pediatric Research Unit

Guys Hospital Medical School

London, England

Dear Dr. Fraser-Roberts:

I have read with interest your Woodhull Lecture, in the Proceedings of the Royal Institution.

I am writing to mention a point presented in the next to the last paragraph of your lecture, which seems to me to be misleading.

I am sure that my statements do not disagree with your own views, but I think that the matter has not been made clear in your lecture.

You mention that the chance that any random pregnancy will end with some severe malformation or other or that some serious error of development will manifest itself in early life is of the order of one in thirty or so.

This statement means that the normal chance of a defective child is 3.33 percent, approximately. You mention also that spina bifida has frequencies varying from one in 250 to one in 500. I might take the normal chance of having spina bifida as one in 375, which is 0.27 present. The normal chance of defects other than spina bifida is then 3.06 percent.

The chance of having spina bifida in a second child, after one has been born with spina bifida, is given as about one in 25, which is 4 percent. Accordingly the chance of some defect in this family is, for each succeeding child, 7.06 percent, which is one in 14.

Earlier in your lecture you say that a risk of recurrence of worse than one in 10 is a bad risk and of not more than one in 20 or 25 is a good risk. I tend to feel that this increase from 3.33 percent to 7.06 percent (both figures approximate, of course) is great enough to justify recommending against the decision to have more children.

My point is that we have to put up with the normal chance of about 3 percent; perhaps we should not accept an added 3 or 4 percent.

Sincerely,

Linus Pauling

LP:jj