the first semester should be Okay, it is the honey moon for freshman, not much homework.
i do not know where you from.
the situation in HK is that, you will have a lot of tests in late Nov and early Dec, the marks include in continuous assestment. No matter, deliver on late Nov or early Dec, you will loose some marks, but you can arrange with the lecturers.
besides, some course only held on either spring/autumn. so cannot defer for 1 semester, you must defer for whole year.
Personally, I would recommend you to defer at least 1 semester or even a whole year. The physical and psychological pressure are very high after you have given birth. So, don't strain yourself, and your baby, too much!
I also had two classmates got pregnant when I was studying postgrad. cert. Both of them defer a few months of study.