Why is Elizabeth Holmes' trial delayed by her pregnancy announcement?

It's because her due date is too close to when the trial was supposed to start. Pregnancy itself isn't a disability, but it can certainly cause debilitating conditions, and even if nothing whatsoever goes wrong, childbirth is still a major medical event. I *really* doubt the judge wants to risk a full-term pregnant woman going into labor in the middle their court room. It's just more practical to push the trial back to a later date.