How many minutes does it take for brain damage to occur if a baby isn't breathing?

It depends: Brain damage does not occur unless there is a significant loss of oxygen and/or other vital nutrients to the brain. Cessation of breathing (apnea) per se does not cause brain damage unless the oxygen level in the blood falls to dangerously low levels for a prolonged period of time. Even if apneic, oxygen levels can be sustained in the blood through other means, for many minutes, or even hours.

Variable: If breathing for the baby is started within a minute and the infant recovers his oxygen saturations and/or he continues to be supported as needed, then no injury has occured. Accumulative long-term apneas resulting in low oxygen can impact brain growth and later development. If baby is found apneic and unresponsive, he may develop hie and require hypothermia therapy to help protect brain.