Sarah Boyle, 26, noticed that her son Teddy had become to 'scream' and refuse milk when she tried to feed him from her right breast.
'He just wasn't having it, even if I gave him a cuddle on that side he didn't like it,' she explained.
Sarah had previously noticed a lump in her breast in 2013, but had had it examined several times and had been told that it was a cyst that wasn't a concern.
However, after Teddy began to become distressed when breastfeeding from the same area, she sought further medical attention and after being referred for a scan and a biopsy, was eventually diagnosed with grade 2 triple negative breast cancer.
Incredibly, the cancer in her cyst had been growing for three months – which was the same time Teddy stopped feeding from her right breast.
'Teddy is my hero,' Sarah said. 'If it hadn't been for him I would never have suspected I had cancer. My consultant told me that breastfeeding helps a mother and baby bond. In my case it did more than that – it saved my life.'
'Teddy could obviously smell and taste that the milk from my right breast tasted different from the milk from my left breast.'
'My consultant said he'd never seen anything like it before and was baffled and amazed. He told me it was very fortunate I chose to breastfeed – otherwise my illness may not have been discovered.'
Sarah has since had to stop breastfeeding Teddy to undergo chemotherapy, which she is currently halfway through. After her treatment, she is planning a double mastectomy with immediate breast reconstruction surgery.
She added: 'I want other women to be aware of any lumps in their breasts and to always get them checked out.'