Pregnancy vs Promotion

I haven’t told my work/boss that I’m pregnant yet, though a few close coworkers who can keep a secret know. I’m up for consideration for a promotion and my plan was to hold off on telling them until I get an answer one way or another since I thought they might subconsciously allow my pregnancy to be a factor in their decision. My question is when should I tell them after they’ve made a decision? Immediately or a few weeks after? I’m 9 weeks tomorrow so I can probably keep hiding it for a bit.