Work Happy Hour when pregnant

Hi there! So I’m looking for advice or excuses anyone has used when attending a work happy hour while pregnant. —> it’s very early in my pregnancy and I’m not telling my coworkers yet. But this week our boss is quitting and her last day, happy hour celebration is Friday. I feel like I have to go, I’ve worked closely with her for 4 years. What do you say when people ask why I’m not drinking? 🧐😐