It could be Melasma. It occurs during pregnancy and persists for long duration. Itis not completely curable but definitely reduced to certain extent. It occurs due to hormonal imbalance and due to sunexposure. So first thing ia you have to use good sunscreen. You can use Suncros tint gel atleast 3 times a day during day time. Use demelan cream for dark spots. apply very little as it can lead to irritation if applied excessivel. There are peels,lasers available for further treatment.