I studied while preg in 2010 (there was tricky times as I had bad morning sickness) but i still put in the work/effort to catch up if i missed a lecture/tute and got a HD - the semester finished June with maybe an exam in July and baby born in August. I wouldn't go any closer than that... You may end up on bed rest if you have high blood pressure, have an early delivery or just be generally feeling crappy/unmotivated.
Also I went back to study when my daughter was 5 months, it wasnt 'easy' as I demand breasted but definitely manageable and got through it ! In hindsight, it's prob easier than studying with a toddler at home!!
Just a tip, make sure u enrol in subjects that will allow for listening to lectures at home so contact time is as little as possible and make sure u have someone who will be available to come over and watch/entertain/put to sleep your bub while you do assignment work or study during the day (even for 4hrs once/wk) cus just thinking you'll do it at night when they go to bed, doesn't always work - they might not be great sleepers in the evening and itll be likely that you're too tired