Meconium

Meconium is the first stool of a newborn. It has a semi-solid consistency and a black-green color. It is composed of swallowed amniotic fluid, lanugo, bile pigments, mucus and exfoliated skin and intestinal epithelia. The amniotic fluid is absorbed from the intestine into the blood and is excreted again in the urine. This mechanism keeps the amniotic fluid clear. The fetal intestinal tract does not contain bacteria.

In some cases, the meconium is prematurely released into the amniotic fluid and thus can be aspirated during labor, a situation called meconium aspiration syndrome (MAS).

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