Black stool during pregnancy first trimester: what to know

Iron commonly darkens bowel movements without causing illness. Food colouring and deeply pigmented foods can do something similar. Bleeding higher in the digestive tract can instead make stool black, sticky, and tar-like, sometimes with an unusually strong smell. Pregnancy does not make this finding safe to ignore. Possible causes include gastritis, Helicobacter pylori infection, or a peptic ulcer, although the stool’s appearance alone cannot identify the cause.

Check whether you take an iron-containing prenatal supplement and note when the colour changed. Do not stop prescribed medicine without discussing it with your maternity clinician. Take a clear description or photograph of the stool if practical, and arrange medical advice promptly, especially if the stool is tarry or the change is unexplained. Keep drinking normally if you can, and avoid taking anti-inflammatory pain medicines unless a clinician has advised them.

Seek urgent care now for dizziness, fainting, marked weakness, fast or irregular heartbeat, vomiting blood or coffee-ground material, severe abdominal pain, or repeated black tarry stools. During pregnancy, also seek urgent assessment for heavy vaginal bleeding, severe one-sided pain, or feeling seriously unwell. These signs can indicate a problem needing examination, blood tests, and treatment rather than home observation.

Ask whether your prenatal supplement could explain the colour, whether your stool sounds tarry, and whether you need blood testing or a stool assessment. Mention vomiting, abdominal discomfort, heartburn, prior ulcers, and every medicine or supplement you use.