Melasma in pregnancy.
Here’s the link to more info on melasma. Since you can’t use any hydroquinones or tretinoin, try to create an almost total light/sun block over these areas. For example, you could use the SkinCeuticals Physical Fusion SPF 50 with Laura Mercier Tinted Moisturizer (SPF 20) over that with Jane Iredale mineral powder (also SPF 20) over that. Reapply the mineral powder every 2-3 hours. When I had melasma in preganancy, I did all that plus I would even add the organic Eminence Vanilla Cream (SPF 32) as a base layer under the Physical Fusion sometimes. It sounds a little crazy but it actually works pretty well.
And, wear a full brimmed hat every time you are outside or in a car!! It really helps. I know it’s a lot of work but you’ll see a difference if you are careful.