Ultimately it's up to you, there's no law keeping you at home. The guidance is there for your protection though, so your decision should be based on what you want to do not what your head is expecting - especially since everything legally is clear that he/she can't expect you to work. .
My decision is based on the fact that although the existing research suggests there's no additional risk, there's also a lack of evidence on the effects on a pregnancy (since it's so new) and for me, it's just not worth the risk. If it was just me I'd be in and volunteering for extra shifts, but the baby is obviously my priority - and my head hasn't even tried to suggest otherwise.