Miss M - I have been wondering about this also.
I drive a company car, and am finishing up work at 36 weeks. When I was determining the date I was going to finish up at work, the boss said something about insurance not covering and I wouldn't be able to drive the car after 36 weeks. When I checked with the others girls in the office they all said when they had checked with insurance companies they were told that as long as their belly isn't touching the steering wheel that it was ok.
I've just bought a car and will check with the insurance company when organising insurance.
I'll be happy to hand the company car back (although sad to have to pay for petrol ) as some days I find driving a manual car a bit difficult.