Risk assessments at work when pregnant

Just looking for a bit of advice, I'm currently 23 weeks pregnant, I informed my manager when I was only 5 weeks as I have an extremely physical job. I work in re homing kennels for dogs which involves walking, training and vet handling dogs with various different behavioural problems, many with aggression and very 'full on'

Not once have they done any form of risk assessment with me, I have now been signed off with back/hip pain. I have only now received a letter from head office acknowledging I'm pregnant and congratulating me, so I'm thinking my manager has not made any attempt to let them know until now.

I live in the U.K. And just wondering if anyone knows where I stand with this??

I was under the impression that your employer have a duty of care to pregnant woman and really feel like I've just been ignored and it's been 'hidden' I'm pregnant.