The Hospital Authority said a 3-month-old baby girl is in need of a life-saving heart transplant after developing a condition of an enlarged heart chamber that has affected blood pumping to the rest of her body.

The Authority has urged the public to actively support organ donations and consider donating the heart of deceased relatives to give new life to others.

It made the call on Friday after the baby, named Whitney, is said to be in critical condition at the paediatric intensive care unit of the Hong Kong Children's Hospital in Kowloon Bay.

She suffers from dilated cardiomyopathy - a heart muscle disease that causes the heart to be unable to pump enough blood due to a weakened heart muscle.

The infant is relying on a ventilator machine.

She is now at the top of a heart transplant waiting list for patients of similar body size, that weigh 6kg to 18kg. Even though it hopes to look for donor with blood type B+ or O+, the authority said other blood types are also suitable.

A spokesperson in a statement added that it will seek help from the mainland as soon as possible.

"When a patient willing to donate an organ has passed away and no suitable patient is identified on the Mainland, the cross-boundary organ donation and matching mechanism will facilitate a transplant in Hong Kong to bring hope to a critically ill patient."