I work in a warehouse. Part of my job is doing scheduling, tracking shipments, and so on at a computer terminal; part of my job involves physically lifting and moving products. I'm pregnant, and my doctor has said I shouldn't lift more than 20 pounds. My company has several "light duty" positions, which are staffed by people who are temporarily unable to meet the physical requirements of their jobs due to back problems and other physical ailments. I asked my manager to give me a light duty position, but he said the company only has three positions and they are all filled right now. Don't they have to accommodate my lifting restriction?
Your employer may not discriminate against you based on your pregnancy. However, unless you live in a handful of states (California, Hawaii, and Maryland to name a few), your employer does not have an affirmative duty to give you a light duty assignment or otherwise provide an accommodation for your work restrictions. Instead, it means your employer must treat you the same way it treats other employees who are temporarily unable to work for other reasons.
Your manager has said that the company's light duty positions are filled. If this is true, and if the company doesn't discriminate against pregnant women in filling these positions, you are likely out of luck. For example, if the company has given light duty positions to pregnant employees in the past when positions are available, and has denied these positions to employees who are not pregnant when positions are not available, it looks like the company is meeting its legal obligations. Again, the company isn't necessarily required to accommodate your pregnancy: It is required only to treat you no worse than employees whose physical restrictions have a different source.
If it appears that the company has been even-handed in granting light duty positions on a first-come, first-served basis, your next question should be: Why are there only three positions? If there's more than enough light duty to go around, you might ask your employer whether an additional position can be created. However, if your company has a legitimate business reason for the three-position limit, it isn't legally required to offer more. For example, if the company has decided that only three employees can be on light duty at any time in order for the company to meet its productivity targets without hiring additional employees or paying overtime, that's a legally valid justification for not adding any more light duty jobs.
Unfortunately, if you are unable to perform your job duties and your employer doesn't have a light duty position available, your employer would be within its rights to terminate your employment. So, your best strategy in this situation is to try to come up with other solutions. Are coworkers willing to pick up the heavy lifting for a while? Can you work part time, doing the job tasks that involve sitting at your desk, while your employer hires someone else part time to pick up your physical tasks? If one of the light duty positions will soon become available, are there other ways to bridge the gap, such as taking time off? Unless your employer has made accommodations like these for other employees who are temporarily disabled, you aren't legally entitled to insist on them. But by working with your employer to solve the temporary problem, you'll have the best chance of keeping your job.