I doubt pregnancy by itself is an exception. There would need to be a reason you think your pregnancy would detract from being able to listen to and consider evidence, eg unable to sit without breaks for a long time, pain when sitting in particular chairs or high blood pressure.
Having said that, I and a number of colleagues are pregnant lawyers, in court a lot of the time and we're fine. I have a 5 day trial starting next week. It entirely depends on the individual and the individual pregnancy though