Pregnant and started new job

Okay so I was 20 weeks when I applied for this position as a foster care case worker which is my dream to do I’m small so I wasn’t showing as much as others and I didn’t mention being pregnant during the interview then I get the job offer and I didn’t start until the following month so now I am 25 weeks and have had three days of work so far but I’m showing more now and it’s starting to be noticeable and this is a high demanding job I want to tell them but I’m nervous as they would judge me and make working here difficult or not like me anymore but i honestly just graduated college and saw the opportunity to apply and I actually got it and would feel dumb not to take this amazing opportunity. How should i word my email to HR and my supervisor so they are aware but not upset?