Level 1: Causes of hemorrhoids during pregnancy. During pregnancy, the increase and compression of the anus, as well as changes in hormonal levels, will cause the blood vessels around the anus to dilate and become congested, thus causing hemorrhoids. In addition, pregnant women are also prone to hemorrhoids due to poor bowel habits, improper diet and other reasons. Level 2: How to prevent hemorrhoids during pregnancy 1. Maintain good defecation habits: avoid excessive exertion and prolonged straining to defecate. It is recommended to defecate regularly every day and try to sit up straight when going to the toilet.