Black Stool During Pregnancy: Causes, Diagnosis and Prevention

Black stool refers to very dark or tarry poop. Stool colour is usually brown or a shade of brown. Black poop can happen any time, but may put a woman under stress if it happens while she is pregnant. With women taking iron pills in the second trimester, the colour of their -can become darker than usual. While black stools around this time are generally not a cause of concern, it's essential for pregnant women to consult with their healthcare provider if they notice persistent black stool. It can hint towards an underlying health issue that requires attention during pregnancy.

Causes of Black Stool in Pregnancy

Discussed below are the common causes of passing black stool in pregnancy: 

• Medications:
  • Iron supplements- These are commonly prescribed during pregnancy and can temporarily turn stool black. This is generally harmless.
  • Antacids containing bismuth subsalicylate- These can also cause black stool.
  • Other medications- Certain antibiotics, chemotherapy drugs, and anti-inflammatory drugs can also cause black stool.
• Gastrointestinal bleeding: 
  • This can be caused by haemorrhoids, ulcers, inflammatory bowel disease (IBD), or gastrointestinal tumours. 
  • Bleeding is considered more serious if accompanied by symptoms like abdominal pain, rapid heartbeat, fainting, or dizziness. This requires urgent medical attention.
• Dietary Causes:
  • Foods like black licorice, blueberries, dark soda, and iron-fortified cereals can temporarily cause black stool. 
  • This quickly resolves once the food is eliminated from the diet.

When to Seek Medical Care

Seek prompt medical attention if you experience black stool along with concerning symptoms like: 

• Abdominal pain
• Nausea
• Vomiting
• Diarrhoea

Black stool with symptoms like dizziness, fainting, lightheadedness or rapid heartbeat signals possible internal bleeding and requires emergency care. It's always better to consult your doctor even if you only have mild symptoms or are unsure of the cause.

Diagnosing the Causes of Black Stool

The doctor will review your medical history, medications, and dietary habits to identify potential causes. Blood tests may be ordered to check for anaemia or issues with your liver, pancreas, or gallbladder.

Further testing like an upper endoscopy or colonoscopy allows visualisation of the gastrointestinal tract to check for sources of bleeding or other abnormalities. Additional imaging tests may be done if cancer is suspected.

Treatment Options

• Medication-related:
  • Your doctor may adjust the dosage of supplements like iron or switch medications if they are causing black stool. 
  • Antacids may need to be avoided completely.
• Bleeding-related:
  • Treatment depends on the severity and location of the bleeding. 
  • Hospital admission, blood transfusions, and surgery may be needed in serious cases.
• Dietary causes:
  • Eliminating problematic foods from your diet can quickly resolve this benign cause of black stool.
• Underlying condition:
  • Treating health conditions like IBD, haemorrhoids, or ulcers may address the root cause of black stools.

Prevention Tips

• Take iron supplements with food to minimise side effects
• Stay well hydrated
• Consume plenty of fibre
• Avoid straining during bowel movements
• Refrain from taking non-steroidal anti-inflammatory medications which can cause stomach irritation

Iron Supplements and Digestive Issues in Pregnancy

Iron aids in transporting oxygen in blood. Low iron causes anaemia which is associated with pregnancy complications. However, excess iron can accumulate in the intestines, causing black stool when it interacts with digestive acids.

Managing the Effects of Iron

• If black stool occurs after starting iron supplements in pregnancy, consult your doctor about lowering the dose or switching formulations, while ensuring adequate iron intake.
• Take iron with vitamin C which aids absorption, and avoid taking it with milk products, tea, or coffee which reduce absorption.
• Start supplements early in pregnancy at lower doses and titrate based on lab testing, which minimises side effects.

Call your doctor if you experience persistent black stool despite changes in iron intake or new symptoms like abdominal discomfort. Seek emergency care if you have a black stool with symptoms like dizziness, chest pain, or fainting which can indicate bleeding.

Other Common Digestive Issues in Pregnancy

• Constipation:
  • Constipation is common due to hormonal changes and pressure from the growing uterus slowing down colonic transit.
  • Drink plenty of water, exercise regularly, and consume high-fibre foods like fruits, vegetables, and whole grains. 
  • Stool softeners or laxatives may occasionally be needed.
• Heartburn:
  • Heartburn occurs from stomach acid backing up through the esophageal sphincter which is relaxed by pregnancy hormones.
  • Identify and avoid heartburn triggers. 
  • Sleep with your head elevated, eat small frequent meals, and avoid lying down after eating. 
  • Antacids may be used when necessary.
• Haemorrhoids:
  • Veins in the rectum and anus swell due to increased blood flow and pressure from constipation and pushing during delivery.
  • Prevent haemorrhoids by avoiding constipation with adequate fluid and fibre intake. 
  • Apply witch hazel pads, ice packs, or warm baths to relieve symptoms.

Importance of Diet and Nutrition in Pregnancy

• Second Trimester Diet
  • By the second trimester, nausea has often subsided, allowing intake of a wider variety of healthy foods.
  • Focus meals around vegetables, fruits, whole grains, beans, lentils, nuts and seeds. This helps provide essential vitamins, minerals, fibre, and plant-based protein.
  • Calcium is critical for foetal bone development. Prioritise dairy products, calcium-fortified plant milks, or leafy greens.
  • Iron is also vital, and deficiency can cause black stools. Boost iron absorption by pairing iron-rich foods with vitamin C sources like oranges, bell peppers, or strawberries. Avoid drinking coffee or tea with iron-rich meals, as tannins can inhibit iron absorption.

Foods to Prevent Black Stools

• Increase intake of iron-rich foods like grass-fed red meat, organ meats, spinach, lentils, pumpkin seeds, and iron-fortified cereals.
• Take iron supplements if the diet is not meeting daily needs, but discuss the correct course with your doctor.
• Stay well-hydrated and maintain soft stools through high fibre foods and probiotic sources like yoghurt.
• Limit antacids as low stomach acid impedes iron absorption.
• Avoid excess zinc supplements as high levels can interfere with iron.

Coping with Health Issues in Pregnancy

• Common Reactions
  • Anxious or worried about what black stool or other symptoms mean.
  • Sad or disappointed health issues are interfering with enjoying your pregnancy.
  • Overwhelmed by medical appointments and treatments on top of usual demands.
• Self-Care Strategies
  • Practice relaxation techniques like yoga and meditation
  • Prioritise proper rest and nutrition
  • Seek support from your healthcare team, partner, friends and family
  • Join a pregnancy support group to connect with other expectant mothers
• Professional Support
  • Your doctor can provide referrals to mental health professionals including pregnancy-specialised therapists or support groups.
  • Talk to your doctor if anxiety or sadness persists or interferes with daily function.
  • Medications and counselling are considered safe during pregnancy when clinically indicated.

Common Misconceptions about Black Stools in Pregnancy

• Black stool always requires treatment: While black stool can indicate an underlying problem, the most common cause in pregnancy is iron supplementation which typically does not require stopping the supplements or additional treatment unless symptoms develop.
• Black stool equals internal bleeding: Gastrointestinal bleeding is one possible cause but many factors like food and medications also cause black stool without bleeding being present. Your doctor determines the cause through testing.
• Ignoring symptoms is safe: While some pregnancy symptoms are benign, others like persistent black stool, fever or bleeding signal potentially serious complications requiring prompt medical attention for the health of both mother and baby. 

Key Takeaways

Contact your doctor any time black stool occurs in pregnancy for evaluation of the cause and possible treatment if indicated, especially if additional symptoms are present. Other problematic symptoms also warrant medical care. 

Prenatal vitamins with iron frequently cause temporary black stool which resolves after dose adjustment without stopping supplements altogether.

A healthy, balanced diet and lifestyle support the optimal development of your baby over the remaining weeks while minimizing digestive issues and pregnancy complications.