Women are far more likely than men to get melasma. It is so common during pregnancy that some people call it the mask of pregnancy. Hormones seem to trigger melasma.
People with darker skin, such as those of Latin/Hispanic, North African, African-American, Asian, Indian, Middle Eastern, and Mediterranean descent are more likely to get melasma. People who have a blood relative who had melasma also are much more likely to get melasma.