Black stool during pregnancy is most commonly caused by iron supplements prescribed to prevent or treat anemia. The unabsorbed iron in these supplements can darken the stool, giving it a black or tarry appearance. This is generally harmless and a normal side effect of iron supplementation.
Other common causes include:
- Dietary factors: Consuming certain iron-rich or dark-colored foods such as spinach, red meat, licorice, or blueberries can also cause dark stools.
- Medications: Some medicines like Pepto-Bismol (bismuth-containing drugs) can lead to black stool by reacting with sulfur in the digestive tract.
- Constipation or hemorrhoids: Common in pregnancy, these can cause bleeding in the lower digestive tract that may alter stool color.
- Gastrointestinal bleeding: Though less common, black stool (called melena) can indicate bleeding in the upper digestive tract (stomach or small intestine) due to ulcers or gastritis. This requires immediate medical attention.
If black stool appears along with symptoms such as abdominal pain, persistent vomiting, weakness, or dizziness, or if it is accompanied by bright red blood, urgent medical evaluation is necessary.
Diagnosis and Management
- Medical history, diet review, and stool tests (including fecal occult blood test) help determine the cause.
- Drinking plenty of water, managing iron intake with a doctor’s guidance, and eating a balanced diet rich in fiber can help prevent constipation and related stool changes.
- Regular prenatal check-ups are important to monitor maternal and fetal health and exclude serious causes.
In summary, black stool in pregnancy is most often caused by iron supplements or dietary changes and is usually not harmful, but it is important to consult a healthcare provider to rule out more serious causes like gastrointestinal bleeding.
