As your body changes with pregnancy, a regular bra won't provide the support you need. Maternity bras are constructed specifically to support breasts that are heavier with pregnancy and to stretch enough to accommodate growing breasts. They have greater cup coverage to keep breasts contained and supported. They usually have at least 3 closure settings, with up to 6 columns. This allows you to start on the tightest closure and loosen it as your breasts grow.
Maternity bras come in a variety of styles, both underwire and soft cup and many women find soft cup to be more comfortable during pregnancy. Either way, look for a band that lays flat on your ribcage, under your breasts. Some styles have wider straps and a u-shaped or leotard back, which can help ease shoulder and back pain. Some soft-cup styles are constructed with inner support bands or side support slings that protect and support breasts. Maternity bras are made in a variety of fabrics. Smooth microfiber is almost invisible under clothing. If you find that pregnancy is causing swings in body temperature, try a maternity bra with moisture-wicking capability or a cotton bra.