Why is there a 50% chance of a woman with down syndrome producing a normal baby?

Downs syndrome: Based on genetics, a women with downs syndrome will have eggs that are either 23 x or 24 x with an extra # 21 chromosome. Therefore there is a 50 % chance that she will pass on a normal 23 chromosome compliment to her fetus.

Its called nature: In deference to the males who are sterile, the females go through normal puberty and can be fertile afterward.During the complex events forming her eggs, two options emerge (50/50).Her eggs can have 23 chromosomes +an extra 21, or just the normal 23.At conception either a DS fetus or a normal one is formed. Since some DS babies will abort, there is potential for > 50% normal at birth.

Laws of genetics: When a woman with Down's Syndrome forms gametes (unfertilized eggs), all the chromosomes except #21 will split evenly. Since Down's Syndrome means three copies of chromosome 21 (by dehfinition), the chromosome cannot split "evenly" - half will have 1 copy (normal); the other half will have 2 copies (Down's syndrome carrier). These will pair with 1 copy (usually) of Chromosome 21 from the father.