I'm pretty sure that giving birth in a vehicle pulled over at the side of the road is pretty dangerous. Ambulances exist, but are expensive in the US.

The point really wasn't that we should allow drunk drivers because wives might give birth: It was pointing out that software won't be able to tell the difference between impaired driving and fairly normal reasons for driving erratically. In other words, they won't know if you are getting a police escort to the hospital (like my parents did when my sister was born) or driving impaired.