Sometimes — before birth or during labor and delivery — a baby inhales a mixture of amniotic fluid and a substance called meconium into his lungs.
This is called meconium aspiration syndrome (MAS), and while it can cause breathing issues, your baby’s care team is well prepared to recognize and handle it. With prompt treatment, most newborns recover fully and go on to breathe easy in no time.
What is meconium?
Meconium is your baby’s first poop. The thick, dark green/black, tar-like substance is a mix of waste products such as cells, protein, and bile.
While you’ll typically see meconium when you change your newborn’s first diapers, sometimes a baby passes it before or during labor and delivery.
What is meconium aspiration syndrome (MAS)?
Meconium aspiration syndrome (MAS) means that an infant breathes the thick and sticky meconium into his lungs just before or during birth. MAS can cause trouble breathing and damaged lung tissue.
Having meconium in the amniotic fluid doesn’t mean your baby has inhaled it, but it’s a heads-up for your baby’s care team to check for MAS.
“I had meconium in my fluid during both my labors,” says What to Expect Community member Gmom0218. “Luckily neither baby aspirated, and they didn’t have any breathing issues.”
According to the National Institutes of Health (NIH), only about 5% of babies with meconium-stained amniotic fluid will have MAS. Some of these babies need help with breathing for a few hours or days.
What causes meconium aspiration syndrome?
If your baby releases meconium and then gasps, he may inhale the mixture of amniotic fluid and meconium.
A baby may release and inhale meconium when under stress due to low oxygen or an infection either in utero or during delivery. Other reasons include:
- A long labor. A tough, extended labor and delivery may up the risk of passing meconium.
- Being overdue. Another factor is a longer-than-usual stay in the womb (more than 40 weeks).
- Maternal health issues. If you have diabetes or high blood pressure or you’ve smoked or used drugs during pregnancy, meconium in the amniotic fluid is more likely.
“My first baby, born at 40.4, had a lot of meconium in the fluid. A lot. But she was just fine,” says What to Expect Community mom Jo9501. “They suctioned her nose and mouth like they do for everybody, but crying was spontaneous and her APGARs were 9 and 10. A NICU team attended the birth but was not needed.”
What are symptoms of meconium aspiration syndrome?
The doctor and nurses on your delivery team will keep close tabs on your baby during labor and delivery, especially if you have one of the potential risk factors listed above.
If your baby inhales meconium, he may have these common MAS symptoms:
- Fetal distress. Breathing trouble such as rapid breathing or grunting while inhaling, low blood pressure, or a slowed heart rate
- Meconium staining. A greenish hue to the amniotic fluid, or a yellowish tint to your baby’s skin, nails, or umbilical cord
- Bluish skin or limpness. A limp appearance, unresponsiveness, or bluish skin or lips
Worried about what will happen during childbirth? The What to Expect app has all the information and reassurance you need about labor, delivery, and beyond, including expert-backed advice and tips from other parents.
How is meconium aspiration syndrome diagnosed?
If your baby has meconium in his amniotic fluid, the doctors will be alert for signs of MAS. They’ll monitor your baby’s heart rate and listen to his breathing for signs of distress.
Other tests to determine if your baby has MAS might include:
- A laryngoscopy to see if there’s meconium staining on the vocal cords (a laryngoscope is a thin tube with a light and camera)
- A chest X-ray to see if there’s fluid in your baby’s lungs
- A blood gas analysis to show how well your baby’s getting oxygen and clearing carbon dioxide
The doctor may run more tests to rule out conditions with similar symptoms, such as pneumonia.
How is meconium aspiration syndrome treated?
Try not to worry too much about MAS, as most babies get better in a matter of hours. In more serious cases, it may take several days or weeks in the NICU. Still, MAS can be successfully treated.
Suctioning a baby’s airways used to be standard care. It’s not clear how much this actually helps prevent MAS, but the doctor may attempt it, as well as some of these treatments:
- Warm and dry care. A special care nursery or NICU team will work to stimulate your baby by tapping on his chest and using a warmer to keep his temperature stable.
- Breathing mask. To help your baby get more air faster, he may wear an oxygen mask to inflate his lungs.
- Antibiotics or an IV. If an infection is the cause of fetal distress, antibiotics can help, and if breathing issues prevent nursing or bottle feeding, IV nutrition is an option.
In more severe cases, a baby may need a breathing tube, a ventilator, or a CPAP machine (continuous positive airway pressure) to aid breathing. Doctors can also administer what's called an artificial surfactant to help keep the lungs' air sacs open.
Can you prevent meconium aspiration?
The best way to prevent meconium aspiration is to stay as healthy as you can during pregnancy and keep all of your prenatal appointments. By sticking to this important schedule, you can update your doctor if you notice anything unusual — and get any necessary testing done right away.
The rates of MAS have decreased over the years, and this is most likely related to OB/GYNs recognizing signs of fetal distress during labor, as well as women following their doctor’s recommendations, says Kyle Monk, M.D., board-certified pediatrician at Cedars-Sinai Medical Center in Los Angeles and a member of the What to Expect Medical Review Board.
For example, if your water breaks and you see greenish-brown stains or streaks in the fluid, call the doctor ASAP. And if your due date comes and goes with no baby in sight, your doctor may recommend labor induction, which may help stave off a case of MAS.
What complications are associated with meconium aspiration?
Most infants with MAS recover quickly and without any long-term health problems.
Some babies with severe MAS may have wheezing and coughing for the first five to 10 years, according to the NIH. And rarely, MAS can lead to permanent lung damage.
Remember: Though meconium aspiration can make those first few moments a little stressful, it’s rarely serious and very treatable. Before you know it, your little one will be taking big, healthy breaths all on his own.
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