A fetus expels waste through the umbilical cord. The umbilical cord is attached to the fetus at the belly button and is attached to the mother's placenta.
The placenta works with both mother and baby to provide blood, nutrients and oxygen to the fetus while in the womb. Once the baby is born, the mother expels the placenta.
The umbilical cord is made of three blood vessels that attach the fetus to the mother. It can grow to be around 23 inches long, which gives the baby plenty of room to move without damaging the cord or placenta or having the cord tangle around the baby.