Unfortunately I don't believe age will be a reason to have you removed from work as although the risk of miscarriage is increased it is due to chromosomal reasons and thus low activity will have no effect. I was taken off work with my last pregnancy at 17 weeks as I have a history of preterm labour, work 12 hour days on my feet and am expected to lift 40lbs. With my previous pregnancies I was told I could still work all day on my feet and just had restrictions put on how much I can lift in the late second trimester, I worked long, stressful days until before labour began.
I can tell you from having been off work, sitting at home is worse than keeping busy.