Is it normal to have uncontrolled bowel movements in your third trimester? if so, why?

No: I wouldn't say that it's normal to have uncontrolled bowel movements. There can definitely be a lot more pressure on the rack them in the third trimester due to the position of the babies head. Definitely mom's express that they feel like they don't have as much time to get to the bathroom. Uncontrolled implies loss of sphincter control or an autonomic nerve problem discuss with your doctor in greater detail.