Final answer:
A pregnant woman should avoid alcohol throughout her entire pregnancy to prevent abnormalities in growth and development. It is crucial to avoid alcohol during the first eight weeks after fertilization, as this is when major organs are forming.
Step-by-step explanation:
A pregnant woman should be advised to avoid alcohol throughout her entire pregnancy. Alcohol can cross the placenta and enter the embryo's or fetus's blood, causing abnormalities in growth and development. It is especially important for her to avoid alcohol during the first eight weeks after fertilization, as this is when the major organs are forming and exposure to harmful substances can cause damage.