Learn About Meconium Aspiration Syndrome

What is the definition of Meconium Aspiration Syndrome?

Meconium aspiration syndrome (MAS) refers to breathing problems that a newborn baby may have when:

  • There are no other causes, and
  • The baby has passed meconium (stool) into the amniotic fluid during labor or delivery

MAS may occur if the baby breathes (aspirates) this fluid into the lungs.

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What are the alternative names for Meconium Aspiration Syndrome?

MAS; Meconium pneumonitis (inflammation of the lungs); Labor - meconium; Delivery - meconium; Neonatal - meconium; Newborn care - meconium

What are the causes of Meconium Aspiration Syndrome?

Meconium is the early stool passed by a newborn soon after birth, before the baby starts to feed and digest milk or formula.

In some cases, the baby passes meconium while still inside the uterus. This can happen when babies are "under stress" due to a decrease in blood and oxygen supply. This is often due to problems with the placenta or the umbilical cord.

Once the baby passes the meconium into the surrounding amniotic fluid, they may breathe it into the lungs. This may happen:

  • While the baby is still in the uterus
  • During delivery
  • Immediately after birth

The meconium can also block the infant's airways right after birth. It can cause breathing problems due to swelling (inflammation) in the baby's lungs after birth.

Risk factors that may cause stress on the baby before birth include:

  • "Aging" of the placenta if the pregnancy goes far past the due date
  • Decreased oxygen to the infant while in the uterus
  • Diabetes in the pregnant mother
  • Difficult delivery or long labor
  • High blood pressure in the pregnant mother
  • Infection in the placenta affecting the baby
What are the symptoms of Meconium Aspiration Syndrome?

Most babies who have passed meconium into the amniotic fluid do not breathe it into their lungs during labor and delivery. They are unlikely to have any symptoms or problems.

Babies who do breathe in this fluid may have the following:

  • Bluish skin color (cyanosis) in the infant
  • Working hard to breathe (noisy breathing, grunting, using extra muscles to breathe, breathing rapidly)
  • No breathing (lack of respiratory effort, or apnea)
  • Limpness at birth
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What are the current treatments for Meconium Aspiration Syndrome?

A special care team should be present when the baby is born if traces of meconium are found in the amniotic fluid. This happens in more than 10% of normal pregnancies. If the baby is active and crying, no treatment is needed.

If the baby is not active and crying right after delivery, the team will:

  • Warm and maintain normal temperature
  • Dry and stimulate the baby

This intervention is often all babies need to begin breathing on their own.

If the baby is not breathing or has a low heart rate:

  • The team will help the baby breathe using a face mask attached to a bag that delivers an oxygen mixture to inflate the baby's lungs.
  • The infant may be placed in the special care nursery or newborn intensive care unit in order to be watched closely.

Other treatments may include:

  • Antibiotics to treat possible infection.
  • Breathing machine (ventilator) if baby is unable to breathe on their own or needs a large amount of extra oxygen.
  • Oxygen to keep blood levels normal.
  • Intravenous (IV) nutrition -- nutrition through the veins -- if breathing problems are keeping baby from being able to feed by mouth.
  • Radiant warmer to maintain body temperature.
  • Surfactant to help lungs exchange oxygen. This is only used in more severe cases.
  • Nitric oxide (also referred to as NO, an inhaled gas) to help blood flow and oxygen exchange in the lungs. This is only used in severe cases.
  • ECMO (extracorporeal membrane oxygenation) is a kind of heart/lung bypass. It may be used in very severe cases.
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What is the outlook (prognosis) for Meconium Aspiration Syndrome?

In most cases of meconium-stained fluid, the outlook is excellent and there are no long-term health effects.

  • Only about 5% of babies with meconium-stained fluid will have MAS.
  • Babies may need extra support with breathing and nutrition in some cases. This need will often go away in 2 to 4 days. However, rapid breathing may continue for several days.
  • MAS rarely leads to permanent lung damage. Some babies with severe MAS may have problems with coughing and wheezing for the first 5-10 years.

MAS can occur along with a rare but serious problem with the blood flow to and from the lungs. This is called persistent pulmonary hypertension of the newborn (PPHN).

How do I prevent Meconium Aspiration Syndrome?

To prevent problems that lead to meconium being present, stay healthy during pregnancy and follow your health care provider's advice.

Your provider will want to be prepared for meconium being present at birth if:

  • Your water broke at home and the fluid was clear or stained with a greenish or brown substance.
  • Any testing done during your pregnancy indicates there may be problems present.
  • Fetal monitoring shows any signs of fetal distress.
What are the latest Meconium Aspiration Syndrome Clinical Trials?
Effect of Adding Metformin to Insulin in Uncontrolled Diabetic Patients During the 3rd Trimester of Pregnancy on Glycemic Control, Fetal and Neonatal Outcomes ,Randomized Controlled Trial

Summary: Background Diabetes mellitus (DM) is a significant contributor to adverse obstetric and perinatal outcome. There is now clear and unequivocal evidence that adverse pregnancy outcomes are strongly linked to maternal hyperglycemia, both in the peri-conception period and throughout gestation. Although strict glycemic control does improve outcomes, there is still a higher rate of complications in wome...

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Pulmonary Function Using Non-invasive Forced Oscillometry Respiratory Testing: A Prospective Observational Study

Summary: The purpose of this observational study is to measure pulmonary function in term and preterm infants with and without pulmonary disease including respiratory distress syndrome, bronchopulmonary dysplasia, transient tachypnea of the newborn, meconium aspiration syndrome, and response to treatments given to newborn infants with lung diseases using a non-invasive airway oscillometry system.

What are the Latest Advances for Meconium Aspiration Syndrome?
A retrospective cohort study of tracheal intubation for meconium suction in nonvigorous neonates.
Clinical features and prognosis of severe meconium aspiration syndrome with acute respiratory distress syndrome.
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Tracheal suction at birth in non-vigorous neonates born through meconium-stained amniotic fluid.
Who are the sources who wrote this article ?

Published Date: November 09, 2021
Published By: Kimberly G Lee, MD, MSc, IBCLC, Clinical Professor of Pediatrics, Division of Neonatology, Medical University of South Carolina, Charleston, SC. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

What are the references for this article ?

Ahlfeld SK. Respiratory tract disorders. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 122.

Crowley MA. Neonatal respiratory disorders. In: Martin RJ, Fanaroff AA, Walsh MC, eds. Fanaroff and Martin's Neonatal-Perinatal Medicine: Diseases of the Fetus and Infant. 11th ed. Philadelphia, PA: Elsevier; 2020:chap 66.