Is constant heartburn an early pregnancy sign?

Not actual indicator: Usually none but could have breast swelling & tenderness, food aversions, nausea. Other sx's that occur in pregnancy include: darkened areolas, thin, white & milky vaginal discharge, fatigue, ^ urination frequency, constipation, bloating, heartburn, backache, cramping, headache, food cravings, ^ sense of smell, enlarged waist, feeling faint/dizzy, mood swings,^ gas, insomnia, gagging & yawning.