'I lost my seven children through mitochondria defect'

Every time Sharon Bernardi became pregnant, she hoped for a healthy child.

But all seven of her children died from a rare genetic disease that affects the central nervous system - three of them just hours after birth.

One of her children, Edward, survived into adulthood but died at the age of 21.

He was given drugs and blood transfusions to prevent the lactic acidosis (a kind of blood poisoning) that had killed his siblings.

Now Sharon is supporting medical research that would allow defective mitochondria to be replaced by DNA from another woman.