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Turns Out Breast Milk Poop & Formula Poop Are *Vastly* Different

When you become a parent, expect to have a lot of crappy conversations. Because each time your beautiful baby makes a bowel movement, you’re going to analyze it and wonder if she’s okay. Believe it or not, there are a lot of differences between formula poop vs. breast milk poop — and it’s important to know what to expect each time your baby does number two in her diaper.

Regardless of whether your baby is breastfed or bottle-fed, her first stool is going to be meconium. “Just like a breastfed baby, a formula-fed baby will pass meconium in the first three days, and the color will be the same for both,” Liza Janda, a certified lactation education counselor, tells Romper. “It will go from black, to dark green to brown.” Still, it’s kind of creepy when it comes out, because of its black and tarry appearance.

Once that first stool has passed, you’ll then see what your baby’s poop will probably look like depending if you’re breastfeeding or bottle feeding her. “The best advice for parents is to look at color and consistency to determine if the stool is normal or abnormal,” Dr. Charnetta Colton-Poole, MD, FAAP, a board certified pediatrician, tells Romper. But how do you even know what you’re supposed to be seeing? Let’s dissect the doody, shall we?


Consistency is key in differentiating formula vs. breastfed babies’ BMs. “The consistency of formula-fed babies’ poop is like peanut butter,” says Janda. “Since the ingredients in formula don’t change from day to day, the smell and consistency also stay the same.” With a nursing baby, though, you might wonder how he got Dijon mustard into his diaper…because that is exactly what his poop will resemble. “Breast milk poop has a mustard yellow color, thin consistency, and a seedy appearance because of the curds in it,” Andrea Tran, an RN and a lactation consultant (IBCLC), tells Romper. You’ll never look at Grey Poopon (er, Poupon) the same way again.

And here’s where color comes into play. Unlike formula babies, a breastfed baby’s poo can take on a varied palette of shades. So if you ate a lot of green veggies earlier in the day, chances are your baby’s stool might have an emerald tint to it. Although you may open your baby’s diaper and see the rainbow from one day to the next, one color you don’t want to see is red. “Your baby’s stool can be any color but should never be red, which could signify blood, or white, which could signify a liver or gallbladder problem,” says Dr. Charnetta.


But where formula-fed and nursing babies’ stools definitely differ is in the smell. Poop from babies who take a bottle has an undeniable funk factor. “Breastfed babies' poop actually has a sweet smell to it and is not foul-smelling,” says Janda. The same can’t be said of formula-fed babies, whose diaper changes might kick your gag reflex into high gear.

Overall, your baby’s poop shouldn’t be too problematic. "A breastfed baby to have about six stools a day on average while formula-fed babies poop once or twice a day," says Janda. But if your baby’s stool becomes harder or thicker, she might be experiencing constipation. Also, if you find that her poo suddenly looks lime-colored, she might have an infection, allergy, a cold, or another side effect caused by teething. Take a pic of the poo and call your pediatrician or consult a lactation consultant for further help, and her poop will be picture-perfect pronto.


Liza Janda, certified lactation education counselor

Dr. Charnetta Colton-Poole, MD, Fellow of the American Academy of Pediatrics

Andrea Tran, RN, International Board Certified Lactation Consultant