Hemorrhoids are relatively common in pregnancy as there is more engorgement in the vascular area (blood vessels) due to pressure and circulation surrounding the baby. Constipation and / or diarrhea are also contributing factors, as well as "straining" to have bm.
On the flip side, and not to scare anyone, just be aware, rectal pain and bleeding may be symptoms of a much more serious problem. One of my former patients had rectal pain and bleeding throughout most of her pregnancy, constantly told by her OB, "just hemorrhoids, you will be fine once the baby is here", and finally four months after the baby was born, she insisted or her OB Dr. "do something", by then she could not sit directly on her bottom. She was referred to a surgeon and one exam, not hemorrhoids, but a RECTAL TUMOR, the size of a grapefruit.
Yes, cancer! She was 41 years old with a new baby and two other children.
Bleeding is a sign of something not right, though it may be a rather benign process, it certainly needs to be checked out.