Final answer:
The common complication of the rubella virus is congenital rubella syndrome (CRS), which can cause birth defects, stillbirth, or miscarriage. Postnatal infections of rubella usually have milder symptoms and rarely cause severe complications.
Step-by-step explanation:
The common complication of the rubella virus is congenital rubella syndrome (CRS), which occurs when a pregnant woman is infected with rubella. The virus can cross the placenta and cause developmental defects in the fetus. This can result in birth defects, stillbirth, or miscarriage. However, postnatal infections of rubella usually have milder symptoms and rarely cause severe complications.