Symptoms of indigestion can begin in the first trimester and worsen towards the end of the pregnancy. It presents as either upper abdominal discomfort, a burning feeling in the chest or actually refluxing acid into your mouth. The main reason for acid reflux is that the valves that normally prevents reflux at the opening of your stomach is incompetent and does not work very well in pregnancy most likely due to a progesterone hormone effect. Acid reflux usually settles quickly following delivery.
The best treatment is the use of anti-reflux agents such as Gaviscon or Mylanta and the use of medication such as Zantac or Nexium. All of these agents are safe to use throughout pregnancy and the dose can be altered depending upon the severity of the symptoms. It is also wise to cut back on certain foods that can exacerbate acid reflux or indigestion.
It is important to actively treat acid reflux otherwise it can result in significant nausea and also in gastritis or ulceration of your stomach or gullet which is best avoided.