Black dark stools during pregnancy can be caused by various factors. One common cause is the consumption of iron supplements, which are often prescribed during pregnancy. Iron can darken the color of stool. Another possible reason is the intake of certain foods like blueberries or licorice that can also affect stool color. However, if you notice tarry or sticky stools accompanied by abdominal pain or vomiting, it could indicate a more serious condition called gastrointestinal bleeding. In such cases, it's crucial to seek immediate medical attention as it may pose a risk to both you and your baby. It's always best to consult with your healthcare provider to determine the exact cause and receive appropriate guidance based on your specific situation.