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Complicated births- Meconium aspiration syndrome

  • By Dr. Ananya Mandal

Although 6% to 25% of newborns have amniotic fluid that is stained dark with meconium, only about 11% of them will have some degree of MAS.

The first stool passed by the newborn is a dark, black or brown colored, semi-solid matter. The baby within the womb floats in a clear or straw-colored fluid called the amniotic fluid. This fluid provides nutrition as well as cushioning to protect the baby from injury. During delivery if the baby is stressed due to lack of oxygen or other factors, the peristalsis or movement of its intestines are augmented. In addition, the anal sphincters that guard the anus opening are also opened. This leads to the baby defecating or passing stool within the womb. In many deliveries, some meconium staining of the amniotic fluid is common. However, cleaning up the baby’s airways and monitoring may protect the baby from any harm.

Meconium is not formed in the baby’s guts before 34 weeks of pregnancy. Babies past their due date are usually at risk of being delivered in a meconium-stained fluid. As the baby is born, it tries to breathe in air for the first time. During this process, it inhales some amount of amniotic fluid. When this fluid contains meconium, both are inhaled together. Meconium-stained amniotic fluid may be inhaled by the baby before or during labour and delivery. If the quantities of the inhaled fluid are more with excess meconium, there is the risk of meconium aspiration syndrome (MAS).

On inhaling this fluid, the lungs fail to breathe and function normally, leading to fluid collection in lungs, narrowing of blood vessels and severe lack of oxygen in the newborn baby. This may cause serious consequences including death of the baby.

What are the causes of meconium aspiration syndrome?

Babies born beyond their due date are at risk of passing meconium and them inhaling it during labour. This condition of MAS is also related to stress at birth. This can be caused by problems in the womb, including infections or by difficulty during birth. This stress at birth leads to decreased oxygen in the baby, leading to gasping. Gasping leads to inhalation of the meconium-containing amniotic fluid.

Other risk factors for MAS include long or difficult delivery, mothers who are smokers or are diabetic with high blood pressure or with respiratory or heart disease. Babies with complications of the umbilical cord and who face poor growth while in the uterus (intrauterine growth retardation, IUGR) are also at risk of MAS.

Symptoms of MAS:

  1. Baby born with breathing problems and gasping.
  2. Bluish skin color in the infant indicating low oxygen.
  3. The skin may also be stained green from meconium.
  4. Baby appears limp at birth due to lack of oxygen.
  5. Dark, greenish staining or presence of meconium in the birth fluid.
  6. If the baby is past its due date, the finger and toe nails may be long.

The severity of MAS is dependent on the amount of meconium the baby inhales as well other factors such as infection of the baby within the womb, when the baby arrives post-date, etc. However, the more meconium a baby inhales, the more serious the condition in most cases.

Diagnosis and treatment:

Fetal monitor can pick up signs of the baby’s distress before birth. At birth, the fluid appears greenish black and stained with meconium. Treatment has to be begun immediately at birth. A laryngoscope is inserted into the baby’s wind pipe to suck out the inhaled meconium. Oxygen is administered once the wind pipe is cleared. The doctor also will listen to the baby's lungs to see if they are filling with air at each breath. Ventilator support may be needed for the baby to breathe adequately. A blood gas analysis test may be ordered to determine if the baby is getting enough oxygen. A chest x-ray may also show patches or streaks on the lungs indicative of MAS.

In addition to oxygenation, other supportive measures of treatment include antibiotics to treat any infections, a body warmer to maintain temperature, and maintenance of nutrition.

Babies with MAS may be sent to a special care nursery or a neonatal intensive care unit (NICU). Most babies with MAS improve within a few days or weeks depending on the severity of the condition.