How can rubella infection during early pregnancy affect a developing embryo?

When a woman is infected with the rubella virus during the early stages of pregnancy, the virus can cross the placenta and infect the developing fetus. This prenatal infection is a significant cause of congenital malformation, particularly when the infection occurs within the first eight weeks of gestation, where the risk of defects is greater than 50 percent.12

The resulting condition, known as congenital rubella syndrome, commonly involves defects of the eye, heart, brain, and large arteries. The risk to the fetus decreases significantly as the pregnancy progresses, dropping to about 20 percent by the 16th week and declining sharply thereafter. Because of these severe developmental risks, it is ethically imperative for women of childbearing age who have not had a natural infection to be immunized prior to becoming pregnant.12