Work and pregnant

So I got offered a job in September but it didn’t start till January. I’m now 12 weeks pregnant and I’ve just told my boss who said she will talk to hr as they may terminate the contract, I know I’m on a 6months probation period but can they terminate it? I’m always on time, I stay late to help the other girls the staff have been telling her how helpful I am and how I’m just getting on with the job, please help