Well no, you absolutely shouldn’t stop pushing for a promotion just because you are pregnant but equally, I wouldn’t hide the fact you are pregnant if a job was to come up. It really wouldn’t look good & I imagine there’d be some concerns upon your return that you weren’t honest.
You’ll be showing soon, so unless one comes up in the next month or so, I’d say it’ll become obvious anyway 🤷🏼♀️
I went for a promotion while on maternity leave (before baby was born) & didn’t get it despite literally doing the job unofficially for a year..
I was quite annoyed but result not surprised as it would have been a nightmare for them to manage as I was taking 14 months off! And baby came along a week later & work was the furthest thing from my mind for a long time! When I went back to work, I was fairly relieved to settle back to a job I knew well & was good at. It was an adjustment working with a child & juggling getting them up, dressed, to childcare, the initial emotion of leaving your baby all day etc etc.,
A year after I returned, the job came up again & I got it. So all’s well that ends well. Took a bit longer but I got there! And I get to do it part time, which was fab of my company. I fell pregnant with my second a month into the new role
I felt pretty guilty but all is fine 
Be honest. It’s the best policy.