"Sun exposure makes melasma more apparent," Downie says, so you have to to be especially vigilant during pregnancy.
• Never expose yourself to UV light without first applying a broad-spectrum (UVA and UVB) SPF 30 sunscreen. Reapply it every two hours.
• Apply a bronzer to the lighter portions of your face to even out skin tone. If the dark patches persist after you give birth, see your dermatologist; topically applied hydroquinone can be effective, as can chemical peels.