WANTED: Pregnant female to start immediately. Typical workday to include staying at home, taking care of yourself, and nesting. Benefits: access to library of pregnancy books, 24-hour free pregnancy hotline, discounted nursery furnishings, and baby supply freebies. Pay competitive to your OB/GYN's annual salary. Signing bonus: on-demand massage professional and late-night craving delivery.
The above position would be ideal for most expectant mothers, but doesn't seem to appear in most want ads. Fortunately, your current employment or job prospect is probably also suitable during your pregnancy, and others can be with little modification. And while there are some hard and fast rules regarding activities pregnant women shouldn't engage in, the most important qualifying factor to determine the best jobs is what you feel comfortable doing.
Having worked through two pregnancies myself, I know from experience that every pregnancy is different, including how it affects you on the job. Even though I worked the same job through both, I found that one of my pregnancies required more adjustments than the other. Most accommodations were the type I could implement myself, such as taking the elevator more often than the stairs, or combining my trips into one to spend less time on my feet, or just asking for help instead of doing any heavy lifting on my own. Some are minor changes that your employer would be happy to make to keep you at work and productive.
Not that technically being "at work" is always a requirement. Many jobs lend themselves well to work-from-home positions, even if only temporarily. Talk honestly with your employer once your pregnancy has progressed to the point where you need some assistance, and be sure to point out your willingness to keep up the good work.
The best jobs for pregnant women do not have to be desk jobs, nor are they limited to light-duty work. A healthy pregnancy shouldn't carry many physical restrictions (though mentally, you may discover that expecting causes occasional "pregnancy brain," a foggy confusion that women report as an interesting side effect of the condition). Of course, if yours is a high-risk pregnancy, all bets are off. Talk to your doctor about the physical tasks of your job and follow any restrictions imposed - for your health and your baby's. Aside from that, if you feel comfortable continuing as a UPS delivery person, go for it (as long as you mind late-term lifting restrictions). Exercise is actually good for you during pregnancy, as it is any other time.
So what are the best jobs? The ones that work for you. Pregnancy is not the time to launch your career in auto painting (powerful fumes) or as a skiing instructor (too much of a fall risk), but the majority of jobs are just fine, or can be easily modified. Just listen to your body, and realize that what's right for someone else isn't necessarily right for you.