Some women develop dark patches — melasma — on their faces when they’re pregnant or taking birth control pills.
An increase in melanin, the substance that gives skin its color, is responsible for these dark patches. Melasma usually fades after delivery or when you stop taking the pill. Prevent pigment changes by wearing sunscreen at all times and avoiding the sun. Melasma can also be treated with chemical peels or topical prescriptions of hydroquinone, retinoids, azelaic acid, kojic acid, or hydroxy acids that lighten the patches. But strict avoidance of sunlight is required.