Yes it is but everyone is different and some ppl get symptoms that other have not just depends on the person
First one I had intestinal cramps with diarrhea a couple of hours before preterm labour started, this one I had intestinal cramps and felt like I needed to but couldn't for a couple of hours before I lost my plug and contractions started. So for me, its common but everyone is different.
There's a lot of things I've heard are common then I ear they are uncommon. I'm not sure how common that is but I could see it being normal. Since your stomach gets upset a lot in early pregnancy, most girls throw up, but diarrhea would make sense. But make sure to drink plenty of water