Reproductive cloining is expensive and highly inefficient. More than 90% of cloning attempts fail to produce viable offspring. More than 100 nuclear transfer procedures could be required to produce one viable clone. Clones have also been known to die mysteriously.

 

Scientists say that humans should not be cloned, and the US is trying to ban human cloning. Many scientists feel it is unethical to attempt to clone humans. Not just becasue about most attempts to clone fail, but 30% of clones born alive are affected by "large offspring syndrome". Several cloned animals have died prematurely from infections and other complications. With so many unknown factors concerning reproductive cloning, the attempt to clone humans at this time is considered dangerous and ethically irresponsible.