I was in the same situation when I first graduated. Though I didn't have to, I decided to tell potential employers that I was pregnant. It was solely a issue of trust, I personally did not feel right withholding that information. I did get hired on.
While pregnant, you could try getting hired on in a different field of nursing and then pursue critical care once your done your mat. leave, this avoids or at least minimizes the dispruption of orientation and what not. I simply mean this for your benefit rather the employers, I would think it hard to orientate, deliver, and be on mat leave for a year and then return back to work with little experience.
Otherwise, best of luck in your decision, and congratulations!!! You are going to meet the most wonderful little person who will make your life an absolute joy (on the most part