Over at Newsbusters, Noel Shepherd caught excessively liberal Olberman displaying that he has no understanding of the causes of birth defects, and those listed as being influenced by prior abortions.  Boy-Keith was trying to imply that the association of abortions with some birth defects suggests  that Palin might have had an abortion.

Abortions can cause damage to the reproductive tract, most particularly increasing the problem of incompetent cervix. This leads to premature births, and the related congenital problems associated with prematurity. There are also some troubles associated with failed attempts to abort medically.

Down Syndrome is most often the result of trisomy 21, (three copies of 21st chromosome). This follows a nondisjunction event, during meiotic division to produce the gametes (sperm or oocytes) , unevenly allocating three copies of that chromosome to a resultant human individual. The entire chromosome need not be involved, There is Robertsonian translocation in which the critical part of the 21st chromosome might be attached to the 14th chromosome for example. This can be displayed phenotypically as down syndrome. There is also a minor mechanism producing Mosaicism, in which uneven chromosomal distribution occurs in cell divisions of the developing embryo.

You can see from the above mechanistic explanations that these have nothing to do with prior abortion events.

The imperfect chromosomal distributions occuring in the cell divisions are associated with pregnancies later in life, and this was the case for Palin’s fifth child, Trig.

Olberman has displayed that he has NO idea what causes Down syndrome, and was too lazy to check before he made a fool of himself.

Anyone with energy and Olberman’s email address,  feel free to forward this to him, if it so amuses you.