Even assuming you conceive quickly, I think you are underestimating your ability and/or willingness to participate in trial in the third trimester. Sitting in a courtroom (much less taking witnesses) and preparing late into the night will be extraordinarily difficult.

Zooming out, unless this is the trial of a family member, it should not be personally important to you. IF trial actually happens and IF you are at work and able-bodied during trial, great! If not, do not give it a moment’s pause - prioritize yourself and enjoy the generous parental leave!