Sydney couple Quinta and Greg Turton were looking forward to the arrival of their second baby, a much wanted younger sibling to their son Finlay.

They were devastated to learn their daughter Poppy had cystic fibrosis, dying from the genetic condition only 26 days after her birth.

Quinta and Greg Turton with their sons Angus, 6, and Finlay, 10.

Finlay, now 10, was healthy and the couple from Chifley in Sydney's south had no idea they were carriers of the faulty gene and had a one in four chance of passing it on to their children.

"It was a heartbreaking, horrible time," Mrs Turton said.