You really don't want to be taking any unnecessary medication while pregnant, and Gluteboost sounds 100% unnecessary.
I'm sorry, but try to think of it this way: Everything that passes through your bloodstream is going into your unborn baby's body.
For the sake of your vanity, is it really worth putting a baby's life or well-being at risk?
I know that these type of Gluteboost pills are marketed on the internet as "safe, herbal and natural" but what the hell is natural about increasing the amount of fat your body needs to store??? (that's essentially what those pills do).
Also look into the way your body distributes fat. It's not just on the thigh and butt... You are going to end up obese, and give your baby health problems. STOP NOW.