A nursing bra is a specialized brassiere that provides additional support to women who are lactating and permits comfortable breastfeeding without the need to remove the bra. This is accomplished by specially designed bra cups that include flaps which can be opened with one hand to expose the nipple. The flap is usually held closed with a simple clasp or hook. Purpose A nursing bra is designed to provide quick and easy access to the breast for the purpose of breastfeeding an infant. It typically has flaps or panels that can be unclipped and folded down or to the side with one hand. Nursing bras can be worn under a variety of outer garments. Changes during pregnancy Measurements for an appropriate nursing bra can be performed by a lactation consultant. Women can choose nursing bras with strong side and undercup support and an extra-wide back for optimal support. Nursing bras usually have up to four rows of hooks in the rear closure to allow the woman to adjust her band size to a limited extent. Experts recommend a soft-cup bra made of a blend of cotton and Lycra with cups that stretch to accommodate changes in breast size. Most women buy two or more nursing bras so they can alternate between them. Small-breasted women who do not usually wear a bra may choose to wear a nursing bra to support their larger breasts or simply to prevent milk from leaking onto their clothes. Breast sizes change A woman's breasts grow during pregnancy, usually 1 to 2 cup sizes, and potentially several cup sizes. A woman who wore a C-cup bra prior to her pregnancy may need to buy a larger bra while nursing. Once the baby is born and about 50 to 73 hours after birth, the mother will experience her breasts filling with milk (sometimes referred to as “milk coming in”) and at that point changes in the breast happen very quickly. Once lactation begins, the woman's breasts swell significantly and can feel achy, lumpy and heavy (which is referred to as engorgement). Changes during nursing To provide proper support and fit, to facilitate nursing, and to avoid engorged breasts or other complications that prevent an infant from nursing effectively, it is important to wear nursing bras that fit well. When a woman wears a bra that is too tight, her milk supply may be reduced, and she can