The survival of a woman shot in the head during the Colorado cinema massacre has been hailed as a miracle after a shotgun pellet traversed the precise course of a brain defect she was unaware she had.

Her remarkable story came as another woman who survived the mass shooting on Friday gave birth in the same hospital where her critically injured husband is in a medically induced coma.

Miracle ... Petra Anderson. Credit:Facebook

According to her family, Petra Anderson, 22, a musician, lived because she had a rare genetic condition that left her with a small channel of fluid running from the front to back of her brain.

When she was shot in the face the projectile followed the exact course of the defect, avoiding vital areas and lodging in the rear of her head. Doctors removed it after five hours of surgery.