What Causes Green Baby Poop?

It can be disconcerting to notice green poop in your baby’s diaper, but it’s usually not a cause for concern. Find out more about what green baby poop means and when to call a doctor.

Noticing green poop in your baby's diaper can leave you wondering about their health and well-being. But thankfully, the occasional greenish stool is normal for a newborn, says Linda Folden Palmer, D.C., author of Baby Poop: What Your Pediatrician May Not Tell You. If your baby is eating enough—and if the green stool doesn't appear at every diaper change—you probably don't need to visit the pediatrician. Keep reading to learn more about the causes of green baby poop.

Why Is My Baby's Poop Green?

Your newborn baby's first poop will be greenish-black and tarry in consistency, according to Dr. Palmer. Called meconium, it consists of everything your baby ingested in the womb, including amniotic fluid, bile, and yup, their own skin cells. Over the next few days, the stool begins to take on an army green color, then it turns mustard yellow (if breastfeeding) or tan-brown (if formula feeding).

Stomach bile gives poop its signature brownish color. When stool (poop) is rushed through the digestive tract too quickly, the bile doesn't get digested, leading to a greenish hue, says Dr. Palmer. Here are some possible causes of green baby poop.

Foremilk-hindmilk imbalance

Breast milk changes over the course of a nursing session. The breasts first produce low-fat and high-sugar "foremilk," which gradually transforms into high-fat, high-calorie "hindmilk" as the breast empties.

If your baby tends to have short nursing sessions or you have an oversupply of breast milk, they may be getting more foremilk than hindmilk. This might also happen if the baby switches breasts too quickly or frequently. Too much foremilk may lead to gassiness and green, frothy stools.

Illness

If the green stool looks like diarrhea or contains mucus, something is probably irritating your little one. "Sometimes babies get a stress reaction, or it could be a stomach bug," says Dr. Palmer. If this happens, maintain your regular feeding schedule as your baby will tolerate it; breast milk provides antibodies that promote recovery and your little one will need to stay hydrated.

Food intolerance

According to Dr. Palmer, a leading cause of green baby poop is a food intolerance—either to something in breast milk or the baby's formula. "The number one ingredient that babies react to is cow's milk," she says, although many other foods, beverages, or medications could cause a reaction. If your baby has a food intolerance, they may also develop eczema and act irritable after feeding.

Green foods

Breastfeeding babies may have green poop if the lactating person eats leafy greens or green food coloring. Once your child starts eating solids, green foods (like peas or spinach) can also tint their stool.

Iron supplements

"Dark green baby poop after the first few days of life is probably from an iron supplement," either taken by the [birthing person] or the baby, says Dr. Palmer.

Insufficient milk intake

If a nursing baby isn't getting enough milk, their stool can turn green. They also won't dirty their diaper regularly (newborns should poop at least 3–4 times each day), won't gain weight, and may act fussy or sleepy. Call your OB-GYN, pediatrician, or lactation consultant right away if you're worried your baby isn't eating properly.

Other causes of green baby poop

According to Dr. Palmer, newborns being treated for jaundice with phototherapy can have green poop. Teething could also promote a greenish hue in stool, since teething babies swallow lots of excess saliva. Finally, "some parents report green poop after vaccinations," adds Dr. Palmer.

When to Visit the Doctor for Green Baby Poop

Worried about bright green baby poop, dark green baby poop, watery green baby poop, mucusy green baby poop, or something in between? Rest assured that, on its own, this type of stool is nothing to worry about. It usually doesn't require any special treatment.

However, you should visit the doctor if your baby displays signs of illness, such as fever, lethargy, or vomiting. You should also let your pediatrician know if your baby is experiencing green poop mixed with diarrhea since this puts your little one at risk for dehydration. Signs of dehydration include decreased number of wet diapers, irritability, lack of tears, dry mouth and lips, sunken eyes, and sunken fontanel (soft spot on head). Finally, alert your provider if you don't think your baby is eating enough at feedings.

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