The best policy when you are pregnant is to double check everything with your doctor since our bodies and needs are so different from one person to another. You might have heard about hydrolyzed collagen pills side effects which is something each person should discuss with their doctor since everything depends on each individual body.
With this being said, collagen is a natural supplement that our bodies contain anyways. Therefore, there’s absolutely no reason to suspect that it might be harmful and, even more, it can prevent some dreaded stretch marks. However, before taking a supplement, have a talk with your doctor just to make sure that everything is ok.