Meconium Stools and Transitioning to Normal Baby Poop

baby having his nappy changed
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How long do babies have those black tarry stools? This is a common question, especially from new dads, because meconium stools are rather hard to clean up.

Meconium Stools

Meconium stools are the large dark, black or greenish-black, thick, tarry, sticky bowel movements that newborn babies have on their first two or three days of life.

It is those combinations of adjectives, especially 'large,' 'thick,' and 'sticky,' that make meconium stools hard to clean up and don't make many new parents look forward to these dirty diapers.

Fortunately, meconium stools do not smell bad. While this was once thought to be due to meconium being sterile, studies have found bacteria in the meconium of healthy babies.

Transitioning to Normal Baby Poop

Meconium stools are quickly followed by transitional stools by the time your baby is three to five days old. These stools are a little looser and are a more greenish-brown color and are the 'transition' to regular milk stools on about day six.

If your baby is still having meconium stools after he is three days old or transitional stools after he is five days old, then that can be a sign that he isn't getting enough to eat and you should talk to your pediatrician right away.

In general, you can usually expect that your baby will have:

  • 3 meconium bowel movements on day two that are likely still thick, tarry, and black
  • 3 bowel movements on day three, with the BMs becoming looser and greenish to yellow in color (transitional stools)
  • 3 yellow, soft and watery bowel movements on day four
  • 3 yellow, loose and seedy bowel movements on day five
  • 3 larger, yellow, loose and seedy bowel movements on day seven (milk or breastfeeding stools)

Again, be sure to talk to your pediatrician if your baby isn't following this pattern.

Failure to Pass Meconium

Although many parents are worried that their babies will just never stop filling their diapers with meconium, some babies have the other problem and simply don't have a meconium stool on their first day or two of life.

Since 99 percent of healthy full-term babies usually have a meconium stool within 24 hours of birth and all healthy babies pass their first stool within 48 hours of being born, not having a stool by day two is a sure sign that something is wrong, such as an intestinal obstruction, meconium ileus (which can be associated with cystic fibrosis), Hirschsprung's disease, meconium plug syndrome, or an anorectal malformation, which can include anal stenosis or an absent anus (anal atresia).

Since they can't pass meconium, many of these babies quickly develop distended abdomens, vomiting, and don't feed well. In addition to a physical exam and simple x-rays, other radiologic studies and tests may need to be done to figure out exactly what is causing a newborn baby to have a delay in passing meconium.

Meconium Staining

Much more common than having a problem in which a baby fails to pass any meconium, a baby may actually pass meconium before they are even born, leading to meconium stained amniotic fluid and a meconium stained baby. Although not dangerous in and of itself, if the baby ingests this meconium stained fluid into her lungs, it can cause Meconium Aspiration Syndrome, a potentially life-threatening lung disorder.

Why do baby's pass meconium before they are born? Although it can sometimes happen normally in a baby who is simply overdue to be born, it can also occur in a baby who is undergoing some kind of stress, such as an infection, or if the baby's mother has high blood pressure, diabetes, pre-eclampsia, oligohydramnios, or if she smokes cigarettes heavily.

If your baby is born with meconium staining, she will likely be closely observed to see if she develops rapid or labored breathing or other problems after she is born.


JIMÉNEZ, Esther, et al. Is Meconium From Healthy Newborns Actually Sterile? Research in Microbiology. Vol. 159, Issue 3, pp. 187-193.

Vain, Nestor E. Oropharyngeal and Nasopharyngeal Suctioning of Meconium-Stained Neonates Before Delivery of Their Shoulders: Multicentre, Randomized Controlled Trial. The Lancet. Volume 364, No. 9434, p597–602.

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