What is the ruling on women wearing brassieres, especially those that make the breasts appear larger, and what brassieres are considered natural?

It is permissible for a woman to wear a bra as long as it is not tight, revealing the size of her breasts, unless it is in front of her husband or she wears loose, modest clothing over it, because a woman is commanded to cover her 'awrah in a way that does not describe her size. Ahmad narrated from Usama bin Zayd that the Prophet, peace and blessings be upon him, said: "Tell her to wear a ghilala (undergarment) beneath it, for I fear it may describe the size of her bones." The Permanent Committee for Issuing Fatwas stated that wearing bras makes women's breasts prominent and a source of temptation, so it is not permissible to appear with them in front of non-mahram men. Sheikh Ibn Uthaymeen said that there is no harm in it as something that beautifies the breast, but an unmarried young woman should not wear it for fear of temptation. As for a married woman who wears it for her husband, there is no harm in it.