This is a harmless mixture of amniotic fluid that your baby has swallowed, digestive secretion and dead skin cells that will form your baby's first bowel movement after birth. (bounty.com)
The very first bowel movements — usually occurring during the first day or two, often when you're still at the hospital — are called meconium. (babycenter.com)
Meconium aspiration syndrome (they may choke on their own first bowel movements because of a lessened amount of amniotic fluid and increased amount of bowel movements in utero) (birthingnaturally.net)