What does it mean if my baby is measuring big for gestational age?

Half bigger/smaller. If you look at the size of babies at any point in pregnancy, the average defines a point where half are bigger & half are smaller. In some respects it is comforting as baby must be getting good nutrition through the placenta. It will bare watching because baby size at the time of delivery may prevent vaginal delivery. I have seen babies 11-15 lb at birth & that can be a problem.
Depends. The average woman is around 5 ft. 3 in tall. If you had two women, one who was 5 ft 10 in tall and another one who was 4ft 11 in tall, you would not say either of these women are abnormal, just outside the average. So a baby that measure big for gestational age is outside the average. What you need to know is by how much is the baby outside the range of average.