It depends on the kind of work you do, e.g. if you do physical work/work with chemicals then these duties should usually be suspended without any impact on pay. In terms of office adjustments, a private space for you to rest during the day if tired, permission for rest breaks/reduced caseloads/as you get further along hybrid or home working dye to impact of travel should be considered if feasible. I would ask for a new DSE assessment as you can get different types of chair/cushions to support you. Stress levels should also be risk assessed carefully and revisited regularly as well as any accessibility issues e.g. does your office building have lifts? If you work with members of the public or do homes visits (I am in probation and specialise in violence against women cases) then client allocations should be looked at carefully in terms or any risk they may pose to you. If you want to prepare in advance you can ask your HR to send you a copy of the risk assessment form so you know what to expect.
Also it's a good idea to request appropriate footrests so you can raise your legs at your desk to reduce risks of swelling if you are seated all day
I asked for a riser desk (we already had one was just a case of moving some things around) so I can stand if needs be but also a doughnut cushion - I also asked to work from home two out of 4 days a week due to the commute to work being tiring - it all depends on what you need really also it can be reviewed later on if you’re still early on in your pregnancy - I did mine at 16 weeks and I’m now 31 weeks so have a better idea of what I need now
I've been pregnant twice while working on an office and not needed to ask for anything but I've been lucky generally. My job doesn't involve site visits or anything like that and I'm mostly sat at a computer so nothing dangerous to me or baby! It'd be nice if they gave you some additional equipment to make sitting at your desk more comfortable. But as a regular office chair isn't a risk to you they likely don't legally have to offer any sort of additional adjustments.