A doctor told me my child may have suffered from hypoxia during my labor and delivery. What is hypoxia and What causes it?

Put simply, hypoxia is a lack of oxygen. 

During labor and delivery,  Hypoxia is usually caused by something which stops or slows down the flow of oxygen and nutrients to the baby through the umbilical cord.  Sometimes the cord can be pinched or knotted.  It can also be wrapped too tightly around the baby’s neck.

When hypoxia occurs during labor,  it will often show up on the fetal monitor machine which monitors mom and baby during labor.