So if a mother has HIV and she becomes pregnant, then that baby will also have HIV. And that's because that virus is small enough to actually cross along that placental membrane. Another type of dangerous virus that can affect that fetus is rubella. So if that woman somehow develops rubella, what that means is this virus is small enough to actually cross across that placental membrane. And once it enters the circulatory system of that fetus, it can cause many damaging effects. So the virus rubella basically interferes with many cellular metabolic processes and that can lead to children that are born with different types of abnormalities.