Causes of heartburn Indigestion is common during pregnancy because of: • Growing baby pressing against your stomach. • Pregnancy hormonal changes, changing oestrogen levels lead to an increase in cortisol levels, which can lead to digestive problems like bloating and even heartburn. • The valve at the stomach entrance relaxes, preventing it from closing as it should. This allows the acidic stomach contents to move up into the oesophagus, thus causing heartburn. • Indigestion can happen if you had heartburn before you were pregnant as well as if you have been pregnant before. • It is more common in the later stages of pregnancy.