Meconium aspiration syndrome
Meconium aspiration syndrome (MAS) refers to breathing problems that a newborn baby may have when:
MAS may occur if the baby breathes in (aspirates) this fluid into the lungs.
MAS; Meconium pneumonitis (inflammation of the lungs); Labor - meconium; Delivery - meconium; Neonatal - meconium; Newborn care - meconium
Meconium is the early feces (stool) passed by a newborn soon after birth. It is passed from the body before the baby has started to digest breast milk (or formula).
In some cases, the baby passes meconium while still inside the uterus. This will happen when babies are "under stress" because their supply of blood and oxygen decreases. This is often due to problems with the placenta or the umbilical cord.
Once the meconium has passed into the surrounding amniotic fluid, the baby may breathe meconium into the lungs. This may happen while the baby is still in the uterus, or still covered by amniotic fluid 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:
Some babies do not breathe the meconium fluid 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:
Exams and Tests
Before birth, the fetal monitor may show a slow heart rate. During delivery or at birth, meconium can be seen in the amniotic fluid and on the infant.
The infant may need help with breathing or heartbeat right after birth, and may have a low Apgar score.
The health care team will listen to the infant's chest with a stethoscope and may hear abnormal breath sounds, especially coarse, crackly sounds.
A blood gas analysis will show low (acidic) blood pH, decreased oxygen, and increased carbon dioxide.
A chest x-ray may show patchy or streaky areas in the infant's lungs.
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, a tube is placed in the infant's airway by a nurse, therapist, or doctor. Suction is used to remove any meconium. This procedure may be repeated more than once.
If the baby is not breathing or has a low heart rate:
Other treatments may include:
In most cases, the outlook is excellent and there are no long-term health effects.
Meconium may be present at birth in the amniotic fluid because there is a serious problem with the blood flow to and from the lungs. This is called persistent pulmonary hypertension of the newborn (PPHN).
Staying healthy during pregnancy and following your health care provider's advice can often prevent problems that lead to meconium being present.
Your providers will want to be prepared for meconium being present at birth if:
Crowley MA. Neonatal respiratory disorders. In: Martin RJ, Fanaroff AA, Walsh MC, eds. Fanaroff and Martin's Neonatal-Perinatal Medicine. 10th ed. St. Louis, MO: Elsevier Saunders; 2015:chap 74.
Waldemar AC, Ambalavanan N. Respiratory tract disorders. In: Kliegman RM, Stanton BF, St Geme JW III, Schor NF, eds. Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier; 2016:chap 101
Wyckoff MH, Aziz K, Escobedo MB, Kapadia VS. Part 13: Neonatal Resuscitation: 2015 American Heart Association Guidelines Update for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2015; 3;132(18 Suppl 2):S543-560.
Review Date: 11/3/2015
Reviewed By: Kimberly G Lee, MD, MSc, IBCLC, Associate 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, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
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