I actually had to drop my classes when I was PG because I had a complicated pregnancy (bleeding, low-lying placenta, etc.). I started up again when Siera was 6-7 months old. It wasn't so bad when she was that little because she was too small to crawl around and grab my things. And she was a good baby so I didn't have much of a problem working my schedule around hers.
Now it's a bit rough since she's 2 and walking and talking. I'm home with her during the day, in class every night (Mon-Thurs). I fit as much homework in as I can whenever I can - weekends, etc. I have a hard time sleeping at night so I'm usually doing homework after she goes to bed. It works for us. I think it varies from person to person and everyone has to figure out what works best for them.
Good luck to you