How does rubella cause deafness?

Rubella, or German measles, can cause deafness primarily when a pregnant woman contracts the virus, particularly during the first trimester. The virus can cross the placenta and infect the developing fetus, leading to congenital rubella syndrome (CRS), which may result in damage to the fetal auditory system. This damage can disrupt the formation and function of structures in the inner ear, ultimately leading to hearing loss or deafness in the newborn. Early vaccination against rubella is crucial in preventing these outcomes.