Final answer:
Rubella impacts fetal development due to the teratogenic effects of the virus, causing developmental defects like heart abnormalities and microcephaly, rather than altering chromosomes or enzyme deletion.
Step-by-step explanation:
The impaired fetal development induced by rubella is primarily caused by the teratogenic effects of the rubella virus when it crosses the placenta during pregnancy. This virus does not induce the formation of a 23rd chromosome, produce toxins, alter chromosome numbers, or delete key enzymes within the brain. Instead, the rubella virus may lead to a variety of developmental defects in the fetus, such as heart defects, microcephaly, vision and hearing problems, and cognitive deficits. Congenital rubella syndrome can be very severe and is particularly likely if the mother is infected during the early stages of pregnancy. This is why prenatal screening for rubella is recommended.