What do you think a "socially acceptable" timeframe between mat leaves is?[AB]

My first was born in early November 2023, so I just returned to work after a 12-month leave on November 1, 2024. It took us a year to get pregnant our first go around, so we started trying again this month.... only find this weekend "surprise! BFP". Based on the ovulation date, that makes me due September 29th. I'm very cautiously excited, and know that we have a long road before I am "in the clear" to announce at work. But I am already nervous about the optics of me taking another leave less than a year after coming back. Especially since one of my coworkers came back pregnant from her 18 month leave and is taking another 18 months, and I heard a few snarky comments made about her (NOT appropriate). I'm not quite in the same position as her, but it does still feel like they are close together so I'm a little nervous about announcing.

There is also the awkard fact that our office gives a pretty generous budget for professional development, and they just approved me to go to a conference in May that will cost them about $6K for me to attend. Do I back out since I know I'll be leaving in the fall for mat leave? I kind of feel like it shouldn't matter that I'll be going on leave again; I'm still entitled to the same rights as every other employee while I'm here, right?