Digestive Development

Meconium Formation (First Bowel Movement)

Meconium, baby's first stool, accumulates in intestines throughout pregnancy.

📅

Development Timeline

Weeks 12-40 and postpartum

Overview

Meconium is the thick, sticky, dark green or black substance that becomes your baby's first bowel movement after birth. It begins forming around week 12 as baby swallows amniotic fluid.

Meconium consists of amniotic fluid, skin cells, lanugo, vernix, bile, and other materials baby has ingested. It accumulates in the intestines throughout pregnancy and is typically not passed until after birth.

Occasionally, babies pass meconium before or during birth (meconium-stained amniotic fluid), which can indicate stress or post-term pregnancy and requires extra monitoring to ensure baby doesn't aspirate it.

🗓️ Week-by-Week Milestones

Week 12

Meconium begins forming in intestines

Week 16

Baby swallowing amniotic fluid regularly

Week 20

Meconium accumulating

Week 28

Significant meconium in intestines

Week 37

Full intestines of meconium

Week 40

Ready to pass after birth

👀 What to Expect

•First diapers contain dark, tar-like meconium
•Takes several meconium poops to clear
•Then transitions to normal newborn stools
•If meconium in amniotic fluid, baby monitored closely
•Usually passes easily after birth

💡 Tips for Parents

✓Meconium is baby's first poop
✓Very thick, sticky, and dark
✓Normal to pass within 24-48 hours of birth
✓If passed in womb, can be problematic
✓Post-term babies more likely to pass before birth
✓Hospital monitors for meconium passage

✨ Amazing Facts

💫

Meconium is sterile - no bacteria

💫

Contains swallowed lanugo and skin cells

💫

Very difficult to clean off baby's skin

💫

The word means "poppy juice" in Greek

💫

Passing meconium before birth can indicate stress