M is for Meconium

Meconium is the first substance that occupies your baby’s bowels. The substances your baby ingests while in utero makes up meconium. It may include: skin cells, lanugo (the fine hair that covers their body in uter0), amniotic fluid, bile (responsible for the coloring of meconium), and water. It is thick, sticky, and almost odorless.

What do I need to know about meconium?

  • Meconium is sticky. For this reason you may want to apply a barrier to baby’s bottom to make clean-up a bit easier. We do not recommend Vaseline or other petroleum products. Coconut oil is a safer alternative.
  • Your baby will pass meconium during the first 3 days of life.
  • It is sterile and does not contain bacteria – that is the primary difference between meconium and stool.
  • Passing meconium in utero can be dangerous.
    • If your baby passes meconium in utero it could indicate that your baby is post-date (and ready to be born) or that your baby is in some form of distress (such as maternal high blood pressure, low oxygenation, placental insufficiency, oligohydramnios, infection, etc).
      • Low blood-oxygen levels cause baby’s muscles to relax, which may be the cause of the pre-delivery bowel movement.
      • If your water breaks and it is mostly clear with some greenish-black specks, your baby likely recently passed his first stool. This causes less of a concern than if your water breaks and it is homogeneously greenish. This is indicative that more time has elapsed since your baby passed the meconium and your baby is at a greater risk of complications.
      • You should call your provider immediately if your amniotic fluid is anything other than straw colored. Note the time your water broke and the color.
  • Your placenta can still be encapsulated if your baby has passed meconium in utero.

Is Meconium Aspiration Syndrome (MAS) something I should worry about?

MAS occurs when baby inhales meconium in utero. It can potentially block their airway, leading to trouble breathing. Your doctor/midwife will clear this blockage with a bulb syringe or, in more severe cases, a breathing tube. Trapped air has the potential to cause hyperinflation of the lung resulting in hyperexpansion of the alveoli and increased resistance during exhalation. Meconium deactivates surfactant (which normally lubricates the lungs), causing resistance during exhalation.

In the US, meconium-stained amniotic fluid is detected in 8-25% of births occurring after 34 weeks. Of these babies, about 10% of them develop MAS (so, approximately 1.5% of all births). More information on MAS can be found here.

More Blogs in This Series

N is for NICU
O is for Oxytocin
P is for Placenta Encapsulation

This article is for informational purposes only. It should not take the place of consultation with your healthcare professional.


Leave a Reply