As a business owner, and speaking solely for myself, I NEVER hire those who have left their previous job without giving some type of notice. It seems thoughtless to me, and that is not the type of person I want working for me. Of course, there are always exceptions.
As a lot have advised, don’t quit until you are absolutely positive that you have another job lined up. Especially since you are pregnant. Most interviewers will work with your schedule, all you have to do is ask.
Best of luck to you with your job search, and also with your pregnancy! 