You can definitely go to HR about this if you wanted to.
It is very unfair. He was totally unprofessional and he should have asked you first if he had any intention to tell it to anyone. However, I feel these things happen often because many people just can’t keep their mouth shut and don’t care about how this will impact others, so personally I wouldn’t have told him and anyone else at work until either it became evident or I had to in order to qualify for maternity leave.
To answer whether you should have explicitly told him not to say anything: Yes, you should have explicitly told him. I'm sorry this happened to you. It sucks. It wasn't his news or place to tell others.
I'm sure this is a breach of confidentiality in the UK! when I told my managers (both male and female with no children themselves) they always asked if it was okay to let HR/their managers know in confidence! Then they would also ask if I had told the team etc yet and when I was planning to!
You should not need to explicitly tell your manager to keep it to himself. Your employer is meant to keep any medical information confidential. Health information is protected by law under GDPR, including pregnancy.
I only tell HR and ask them to keep it confidential. I tell colleagues and my line manager at 14 weeks. People can’t keep news to themselves. If I’m ill with pregnancy then I just call in sick or wfh
Being in HR myself, this isn’t a news for him to share with anyone without your consent. You should raise this with your HR or relevant teams as he needs to be told and do any damage control if there is as a result of him over sharing.
I’d be fuminggggggggg!!! Please take this to HR???
My mangers did the exact same thing, not there place or news to discuss. Sorry that happened to You