Depends on when and how much. In the third tri you might lose a lb or two but that is likely due to water weight. It might also make a difference depending on what your weight was prior to pregnancy; like if you started off morbidly obese then this may be less of an issue than if you started off underweight. If your weight loss has been drastic (like maybe more than 6 or 7+ lbs in one week) you might want to consider contacting your doctor/midwife.
Just make sure you're eating healthy and drinking tons of water.
Like PP said, it's normal to lose a couple pounds in your third tri, especially at the end as you're getting closer to delivery. But, if it's a significant amount, 6-7+ from PP is a good number, I would definitely bring it up to your doctor.
Re: Me
Just make sure you're eating healthy and drinking tons of water.
DS2 due 12/12/18