Last night my sim couple gave birth to twin girls at the hospital. Mum took the first baby home in her car, leaving Dad standing on the curb holding baby number 2. He kept standing there, so I told him to go home--and this is what happened when he tried to take baby home on his motorcycle (sorry that I didn't get a closeup, but this happened very quickly):
That's not a pink loaf of bread in his hand.
The game didn't let him drive home like that. The motorcycle disappeared immediately and Dad resumed standing on the curb with baby. I had to remove the motorcycle from his inventory and replace it with a sensible family car. Then he could drive home with the baby velcroed to the steering wheel in accordance with Sim safety standards.