What increases a person's risk for cri du chat syndrome?

Risk factors for cri du chat syndrome include a parent with a chromosome 5 abnormality. However, most of the cases of the syndrome occur when the chromosome in either the egg or sperm breaks randomly prior to fertilization. Scientists are not sure why most of these abnormalities occur. In 80% of the cases, the chromosome abnormality comes from the male's sperm rather than the female's egg.