Pregnant and work!

I recently just started a new job working for the city. I got pregnant two weeks into my job! I’m now 9 weeks and no one knows yet. My

Probation is up in 660 hours so I’m looking at October-November . I’m just worried that they will can me before my probation is finished because I will be going on maternity leave before even working here for a year. They need the staff but I’m still worried. Not sure if I’m just overthinking it or not. My

Job is physical as well so I didn’t really want to wait a couple more months to tell them. I’m

Unionized as well. My boss is really easy going not sure if I should talk to him or not? Ahhh.. Anyone else in similar position or have some advice? Thanks.