Mum-of-five Sam Davies, had lived with the blemish on her forehead for all her life.
And despite being bullied about the mark by school mates who called her "the unicorn" she thought nothing more of it.
However, after the blemish burst, the 31-year-old discovered what three tumours underneath.
During her first four pregnancies Sam said her birthmark would flare up.
However, Sam said when she was expecting a son, the bump on her skin “went out of control”.
She told The Sun: “As my bump grew, the birthmark grew too. It was like a monster. My doctors believe that the male hormones from carrying a boy were the trigger."
Sam was rushed to hospital after losing a lot of blood and was immediately taken to surgeons to stitch up the wound.
She was monitored until her son, Paul Jnr, was born in March 2013.
Doctors carried out life-saving surgery that left part of her skull exposed.
A year later Sam is still awaiting reconstructive surgery, but she says she is finally “pain free”.