A mother-of-four discovered that her husband had slept with her best friend after the woman gave birth and the newborn baby had the same birthmark as her own son.

Sharing her story on TikTok, Hailey, @haileymae93, was asked by her pregnant friend to attend the delivery and she gladly accepted the invitation.

But she was in for a shock as a few days later, when she was helping to change the baby, she found two hereditary birthmarks – which her son also has, as they were passed down by her husband.

Hailey then confronted the mother about the affair – and she admitted it, saying that the baby did belong to her now ex-husband.

She said she noticed what she called the “bowling bumps” on the baby girl’s neck while changing her nappy.

“Several of his other children have it as well, so I knew exactly that the baby was my husband’s at the time.”

Later, the woman said her then-best friend admitted the affair and that she had been sleeping with her husband.

Recalling the moment, she said: “She was standing next to me when I was changing the baby, that’s when we both saw the birthmark.

“We looked at each other, I had to step outside – I needed a moment to think what I should do in this situation.

“She did admit it right away but it wasn’t until six, seven months later my ex-husband did admit that they had been sleeping together.”

She split with her husband sometime later but she and her friend “remained on good terms”, adding that “at the end of the day, her daughter is my children’s sister”.