Skip to main content
Birth Injury Meconium Aspiration Syndrome
  • Home  / 

Meconium Aspiration Syndrome Medical Malpractice

What Is Meconium Aspiration Syndrome?

Meconium aspiration syndrome (MAS) occurs when a newborn inhales a combination of the surrounding amniotic fluid (bag of water) and meconium while still inside the uterus or immediately after birth. Meconium is a newborns first bowel movement or discharge that consists of intestinal cells, mucus, fetal hair, secretions such as bile, proteins, fats, and water. Meconium normally comes out after the baby is born. Its appearance is tarry, greenish in nature, and has a sticky consistency. It has no bacteria which differentiates it from the normal stool.

Approximately 8-25% of all births after 34 weeks of gestation have meconium-stained amniotic fluid, but only 10% of those develop MAS. The incidence is going down in developed countries due to improved prenatal care and birthing facilities. Meconium-stained amniotic fluid is more common in babies at or beyond their due date and those in breech (feet first) positions.

Causes of Meconium Aspiration Syndrome (MAS)

Factors that increase the risk of meconium passage in the uterus are:

  • Placental dysfunction
  • Maternal hypertension
  • Preeclampsia known as “toxemia” which is high blood pressure and kidney dysfunction that leads to protein in the urine 
  • Low amniotic fluid
  • Maternal drug abuse such as cocaine or cigarettes
  • Maternal infection/ Fetal hypoxia (lack of oxygen)
  • Acidosis (low pH in the blood) from lack of oxygen

How Does MAS Affect the Baby?

It is the lack of oxygen that triggers the nerves to relax the anal sphincter which releases the meconium. Meconium in the amniotic fluid is toxic to the skin and lowers the bacterial resistance. The most severe complication is when a baby inhales or aspirates the stained fluid into their lungs. This limits the oxygen intake into the blood via four mechanisms:

  1. Obstruction of the airway such as would occur with choking, which may lead to lung rupture with trapping of air around the heart or other nearby tissues.
  2. Dysfunction of the surfactant that coats the air sacs to allow them to expand with oxygen. This causes the air sacs to collapse, which leads to lowered oxygen and respiratory distress.
  3. Chemical-induced pneumonitis—a form of pneumonia. Enzymes in the meconium act much like gastric acid and harm the developing air sacs by causing massive inflammation. The ability to exchange carbon dioxide for oxygen is greatly diminished.
  4. Elevated blood pressure in the lung vessels, which causes thickening of the walls. This further diminishes the oxygen levels in the blood pumped from the heart.

Signs and Symptoms

Symptoms of respiratory distress include the following:

  • Grunting
  • Nasal flaring
  • Rib cage breathing
  • Fast breathing
  • Blue lips and nail beds (due to low oxygen)
  • Abnormal lung sounds heard on the stethoscope
  • Yellow-green tinge to the skin, nails, and umbilical cord
  • Green urine

Diagnosis

The laboratory tests reveal an abnormal level of acid in the blood and require continuous monitoring of oxygen levels by a process and device called pulse oximetry. Blood levels of electrolytes such as sodium, potassium and calcium, are measured because kidney dysfunction may occur in MAS. A complete blood count is collected to measure the levels of hemoglobin which is the substance responsible for carrying oxygen in the blood, platelets, and white blood cells. 

A condition known as polycythemia is when the blood is thickened with extra red blood cells and may indicate that there was diminished oxygen chronically or in the past that may have caused MAS earlier in the pregnancy rather than during labor and delivery. 

Chest x-ray confirms the diagnosis, locate the areas of lung collapse, leakage, and confirm that all devices such as endotracheal tubes are in their correct location. An ultrasound of the heart (echocardiography) is performed to ensure there are no anatomic defects and that the heart is functioning normally. It can also measure the degree of lung hypertension. A lung ultrasound in MAS can show the severity of the lung collapse, fluid collections around the lungs, and other disturbances consistent with MAS.

A brain CT or MRI may be administered once the baby is stable or if there are neurologic changes that occur. 

Prevention

The best way to prevent MAS is to identify risk factors such as fetal distress and take preventative action. Conditions such as placental insufficiency, low amniotic fluid, and high blood pressure are also contributing risk factors for fetal distress. Continuous fetal monitoring is the best way to detect fetal distress in labor. 

Amnioinfusions used to be commonly employed to make the meconium less thick. They entail inserting a soft, hollow tube into the uterus after the water is broken and infusing warm saline into the cavity. Theoretically, less thick or chunky material would be better tolerated, if aspirated. Studies have failed to prove its usefulness in preventing MAS.

Routine suctioning after birth is no longer recommended nor is inserting a finger into the mouth. This behavior can trigger the gag reflex, which could make matters worse. Gentle bulb suctioning is sufficient to clear secretions. Likewise, the chest of the baby should not be squeezed to force meconium out of the lungs, esophagus, or mouth.  

The American Academy of Pediatrics (AAP) Neonatal Resuscitation Program Steering Committee and the American Heart Association (AHA) recommend the following guidelines for the management of meconium stained fluid. 

  • If the baby is vigorous as in good muscle tone and normal breathing efforts, only bulb suction is needed.
  • If the baby is not vigorous as in poor tone and breathing efforts; warm the baby, clear secretions with bulb suction, dry, stimulate movement, and reposition the head.
  • The principles are the same as for a newborn without meconium

Management and Treatment Guidelines

Neonatal intensive care unit (NICU)

The principals for optimal care include:

  • Maintain body temperature
  • Minimize handling to reduce agitation
  • Sedation may be needed
  • Continuous monitoring of oxygen status and pH
  • Continuous oxygen supplied via a hood or by positive pressure ventilation
  • Mechanical ventilation may be needed in up to 30% of babies with MAS
  • Consider surfactant supplementation as it has been shown to decrease the severity of the disease, need for more invasive procedures and shortens the hospital stay.
  • If there is pulmonary (lung) hypertension, inhaled nitric oxide can open up the air ways
  • Maintain blood pressure in other organs with infused fluid, transfusions, or drugs that tighten up the arteries.
  • Antibiotic use is controversial if there is no evidence of infection
  • Consultations with cardiologists and neurologists are helpful
  • Transfer to a regional Level III NICU may be necessary
  • No feeding in the early stages of MAS

Surgical Care is rarely needed unless severe air leakage or fluid collections cannot be managed with draining tubes or fibrin glue.

Medication Summary

  • Surfactant to replace that which was stripped by the meconium and because it acts as a deterrent to break up meconium particles
  • Drugs to raise blood pressure and open airways called vasoconstrictors consist of dobutamine, dopamine, and epinephrine. 
  • Sedative drugs reduce oxygen requirements and improve ventilation
  • Analgesics such as morphine, fentanyl, and phenobarbital may be helpful for agitation.
  • If sedatives fail, skeletal muscle paralysis may be needed to improve ventilation by the addition of drugs, pancuronium or vecuronium

Complications

The overall complication rate in the United States for MAS is approximately 1.2%, but the mortality rate for severe residual lung disease and pulmonary hypertension is high at a rate of 20%. Air leak syndromes and emphysema can occur in 10-30% of babies with MAS. The neurologic disabilities, if present, are not due to the MAS itself, but from the underlying cause such as chronic oxygen deprivation and pH changes that can occur well in advance of the labor process. Fetal distress can occur before labor or during the labor and birthing process. 

References

  1. Singh BS, Clark RH, Powers RJ, Spitzer AR. Meconium aspiration syndrome remains a significant problem in the NICU: outcomes and treatment patterns in term neonates admitted for intensive care during a ten-year period. J Perinatol. 2009 Jul. 29 (7):497-503. [Medline].
  2. Janssen DJ, Carnielli VP, Cogo P, et al. Surfactant phosphatidylcholine metabolism in neonates with meconium aspiration syndrome. J Pediatr. 2006 Nov. 149 (5):634-9. [Medline].
  3. Wiswell TE, Tuggle JM, Turner BS. Meconium aspiration syndrome: have we made a difference?. Pediatrics. 1990 May. 85 (5):715-21. [Medline].
  4. Yoder BA, Kirsch EA, Barth WH, Gordon MC. Changing obstetric practices associated with decreasing incidence of meconium aspiration syndrome. Obstet Gynecol. 2002 May. 99 (5 pt 1):731-9. [Medline].
  5. Balchin I, Whittaker JC, Lamont RF, Steer PJ. Maternal and fetal characteristics associated with meconium-stained amniotic fluid. Obstet Gynecol. 2011 Apr. 117 (4):828-35. [Medline].
  6. Ghidini A, Spong CY. Severe meconium aspiration syndrome is not caused by aspiration of meconium. Am J Obstet Gynecol. 2001 Oct. 185 (4):931-8. [Medline].
  7. [Guideline] Wyckoff MH, Aziz K, Escobedo MB, et al. Part 13: Neonatal resuscitation: 2015 American Heart Association guidelines update for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2015 Nov 3. 132 (18 suppl 2):S543-60. [Medline].
  8. American College of Obstetricians and Gynecologists. ACOG Committee opinion no. 689 summary: delivery of a newborn with meconium-stained amniotic fluid. Obstet Gynecol. 2017 Mar. 129 (3):593-4. [Medline].
  9. ACOG Committee Obstetric Practice. ACOG Committee opinion number 346, October 2006: amnioninfusion does not prevent meconium aspiration syndrome. Obstet Gynecol. 2006 Oct. 108 (4):1053. [Medline].
  10. Velaphi S, Vidyasagar D. Intrapartum and postdelivery management of infants born to mothers with meconium-stained amniotic fluid: evidence-based recommendations. Clin Perinatol. 2006 Mar. 33 (1):29-42, v-vi. [Medline].
  11. Hofmeyr GJ, Xu H. Amnioinfusion for meconium-stained liquor in labour. Cochrane Database Syst Rev. 2010 Jan 20. CD000014. [Medline].
  12. Fraser WD, Hofmeyr J, Lede R, et al, for the Amnioinfusion Trial Group. Amnioinfusion for the prevention of the meconium aspiration syndrome. N Engl J Med. 2005 Sep 1. 353 (9):909-17. [Medline].
  13. Committee on Obstetric Practice, American College of Obstetricians and Gynecologists. ACOG Committee opinion no. 379: management of delivery of a newborn with meconium-stained amniotic fluid. Obstet Gynecol. 2007 Sep. 110 (3):739. [Medline].
  14. Vain NE, Szyld EG, Prudent LM, Wiswell TE, Aguilar AM, Vivas NI. Oropharyngeal and nasopharyngeal suctioning of meconium-stained neonates before delivery of their shoulders: multicentre, randomised controlled trial. Lancet. 2004 Aug 14-20. 364 (9434):597-602. [Medline].
  15. Chettri S, Bhat BV, Adhisivam B. Current concepts in the management of meconium aspiration syndrome. Indian J Pediatr. 2016 Oct. 83 (10):1125-30. [Medline].
  16. Wiswell TE, Knight GR, Finer NN, et al. A multicenter, randomized, controlled trial comparing Surfaxin (Lucinactant) lavage with standard care for treatment of meconium aspiration syndrome. Pediatrics. 2002 Jun. 109 (6):1081-7. [Medline].
  17. Dargaville PA, Mills JF. Surfactant therapy for meconium aspiration syndrome: current status. Drugs. 2005. 65 (18):2569-91. [Medline].
  18. El Shahed AI, Dargaville PA, Ohlsson A, Soll R. Surfactant for meconium aspiration syndrome in term and late preterm infants. Cochrane Database Syst Rev. 2014 Dec 14. CD002054. [Medline].
  19. Abman SH, Kinsella JP. Inhaled nitric oxide therapy for pulmonary disease in pediatrics. Curr Opin Pediatr. 1998 Jun. 10 (3):236-42. [Medline].
  20. Sarkar S, Hussain N, Herson V. Fibrin glue for persistent pneumothorax in neonates. J Perinatol. 2003 Jan. 23 (1):82-4. [Medline].
  21. El Shahed AI, Dargaville P, Ohlsson A, Soll RF. Surfactant for meconium aspiration syndrome in full term/near term infants. Cochrane Database Syst Rev. 2007 Jul 18. 2:CD002054. [Medline][Full Text].
  22. [Guideline] American Heart Association, American Academy of Pediatrics. 2005 American Heart Association (AHA) guidelines for cardiopulmonary resuscitation (CPR) and emergency cardiovascular care (ECC) of pediatric and neonatal patients: neonatal resuscitation guidelines. Pediatrics. 2006 May. 117 (5):e1029-38. [Medline].
  23. Dargaville PA, South M, McDougall PN. Surfactant and surfactant inhibitors in meconium aspiration syndrome. J Pediatr. 2001 Jan. 138 (1):113-5. [Medline].
  24. Glantz JC, Woods JR. Significance of amniotic fluid meconium. In: Creasy RK, Resnick R, eds. Maternal-Fetal Medicine. 4th ed. Philadelphia, Pa: WB Saunders; 1999. 393-403.
  25. Soll RF, Dargaville P. Surfactant for meconium aspiration syndrome in full term infants. Cochrane Database Syst Rev. 2000. CD002054. [Medline].
  26. Usta IM, Mercer BM, Aswad NK, Sibai BM. The impact of a policy of amnioinfusion for meconium-stained amniotic fluid. Obstet Gynecol. 1995 Feb. 85 (2):237-41. [Medline].
  27. Yeh TF. Core concepts: meconium aspiration syndrome: pathogenesis and current management. NeoReviews. Sep 2010. 11(9):e503-12. [Full Text].
  28. Young TE, Mangum OB. Neofax: A Manual of Drugs Used in Neonatal Care. 11th ed. Bethesda, M: American Society of Health-System Pharmacists; 1998.
  29. von Bahr V, Hultman J, Eksborg S, et al. Long-term survival and causes of late death in children treated with extracorporeal membrane oxygenation. Pediatr Crit Care Med. 2017 Mar. 18 (3):272-80. [Medline].