A police officer has been charged and his employment status is under review after a crash left Sydney woman Gai Vieira in a coma.

Police said the officer had been pursuing another driver who was using a mobile phone in Cronulla on September 5 when the crash occurred.

Gai Vieira was seriously injured in a crash with a police car in Cronulla on September 5.

Police had previously said the officer was travelling at a speed of 124km/h in a 70km/h zone without flashing lights or sirens, when the police vehicle and Mrs Vieira's Mercedes collided.

Mrs Vieira suffered broken bones, punctured lungs and head trauma in the crash.