Can You Deliver Your Way to the Carpool Lane?

I've already discussed the risk of having to deliver our baby on the Bay Bridge (since we're living in Berkeley and traveling to a hospital in San Francisco). Now I'm wondering if we can derive some kind of benefit from this.

Namely, carpool-lane eligibility.

Sure, we've all seen the stories of pregnant women who try to use the carpool lane. Here's one in Arizona. As far as I know, none has been successful.

But what if you're fully dilated? I've heard that police count heads when they're checking for carpool scofflaws. If you can see a bit of the head, are we OK?

Note: The Bay Bridge requires THREE people to use the carpool lane, so I would have to be there too.