A pregnant woman thought her worst nightmare was about to come true when she felt contractions while stuck in heavy traffic until the police sprang to her rescue.

Worried that she might give birth in her car, the woman's mother called the police at 11.45am yesterday.

She was escorted out of the traffic jam on the Greenbridge roundabout, near Oxford Road to Princess Margaret Hospital. A police spokesman said the woman arrived safely at the hospital just after midday and was today awaiting news of her condition.