Hey Olivia,
Yes, it is absolutely normal to experience heartburn instances during pregnancy. It is like any other sign of pregnancy. The growing uterus leads to constipation, indigestion and other gastric problems. Due to the elevated levels of progesterone hormone in the body during pregnancy, the GIT lining and the smooth muscles of uterus relaxes which slows down the digestion process. This relaxation of the muscles also leads to the back flow of the gastric acid causing irritation and burning sensation in the stomach.