You can’t judge whether you’re going to have a baby just by the painful anal distension. If you reach your due date, you have anal distension, increased vaginal discharge, regular contractions, or redness, it’s a sign that you’re going to have a baby. If the pain is simply anal distension, it is due to the enlargement of the fetus and pressure on the rectum, which can cause anal distension, or cause poor bowel movements that can lead to hemorrhoids, which can also cause anal distention and pain.