Wearing a bra under a leotard is not recommended unless you have to. Bra lines will show through a leotard, making them less flattering and reducing the elegant and attract effects that a leotard creates. However, if you have large breasts and need the support during activity, such as ballet, you might need to consider wearing a bra. Try and match the style of the bra to that of the leotard. For instance, if you are wearing a racerback leotard, consider wearing a racerback bra to help hide the straps.