If you've never experienced the discomfort of heartburn before, there's a chance that pregnancy will be your introduction. Changing hormone levels slow down your digestion system, and an expanding uterus can crowd your stomach, pushing acids upward, according to WebMD.
What You Can Do: Don't lie down right after eating, and when you do sleep, keep the head of your bed elevated. Eating small meals more frequently and slowly can also help. This is one case in which your doc may approve Tums, Maalox, or Mylanta — just ask first.