1) Mocktails
This can be a bit tricky because you might not want anyone to witness you ordering a near-beer or a tequila-free margarita, but it can work fine if you can go up to the bar by yourself.
2) Fake it
A regular Coke looks the same as a Jack & Coke. Same thing for 7-Up and a vodka tonic. Or try ordering a water at the same time as a real drink, just sip the water instead.
3) Double upOrder the same drink as your spouse and let him double-fist it. Why not let him have a little extra fun since you're stuck being the designated driver anyway.
4) Be a supportive friend
Hang out with other obviously pregnant ladies or recovering alcoholic friends and share in their non-drinking status to show your "support".
5) The old imaginary illness trick
No one can drink if they're taking antibiotics or cold medicine! Invent a fake illness accordingly, but try not to get too creative. The run of the mill sinus infection or migraine will do.