Thanks for the query.
Skin care needs to be customized based on the presenting complaints.
Based on your description, it appears that you have facial melanosis which could be melasma compounded by acanthosis nigricans. These conditions have a strong relation to one's internal health and it needs to be evaluated as often quoted - Skin is the mirror of internal health. Attempting treatment without understanding the pathology will be futile and make the course longer. Your dermatologist will decide a treatment plan for you after a consultation which probably will include a retinol based night cream and a vitamin C based lotion. I suggest to wait till delivery and then start treatment to reduce any interactions.
Your dermatologist will decide a treatment plan for you after a consultation.
Sun protection is mandatory and will require usage of Sunscreens