What is the name of the first stool of a newborn, which is greenish-black with a tarry consistency?

The first stool of a newborn is referred to as meconium. This substance is distinctive due to its greenish-black color and tarry consistency, which is a result of the accumulation of amniotic fluid, bile, mucus, and intestinal cells that the baby ingested while in the womb. Meconium is typically passed within the first 24 to 48 hours after birth and serves as an important indicator of the newborn's health and gut function. It shows that the digestive system is beginning to function properly as the infant transitions from a fluid-filled environment to feeding outside the womb.

Other terms in the options relate to different aspects of newborn nutrition or digestive processes. Colostrum is the first form of milk produced by the mammary glands and is rich in antibodies but is not a type of stool. Bilirubin is a substance produced from the breakdown of red blood cells and can lead to jaundice if levels are too high, but it is not a stool type. Chyme refers to the semi-fluid mass of partly digested food that is expelled from the stomach into the small intestine during digestion, not relevant in the context of newborn stool.