meconium

a baby's first feces or bowel movement, poop

A greenish-brown substance that comes from a baby's digestive tract and is ordinarily passed after delivery as the baby's first stool. Sometimes, the meconium is passed before birth, in which case it stains the amniotic fluid, turning it greenish brown.

membrane(s)

a very thin layer of tissue that covers a surface

the sac that surrounds the baby in the uterus and contains amniotic fluid in which the baby floats. Also called the bag of waters or amniotic sac, the membranes will rupture naturally or be ruptured artificially during labour