Is it safe to wear foundation underwear during pregnancy?
Yes. Wearing a piece of Lycra like spanx “shapewear” over your bottom, belly, or thighs won’t hurt your baby, regardless of how far along you are. Your baby is well cushioned by the amniotic fluid, and the mild compression of your belly from one of these garments won’t cause any harm.
That said, “regular” Spanx or body shaper might not be the most comfortable choice for your growing body. If it feels okay to you, go for it. Otherwise, you might try the brand’s maternity line, Mama, or seek out maternity shapewear or support products offered by other manufacturers.