Cesarean section is very common nowadays in pregnancy. Following c-section, darkening of skin colour occurs due to excessive production of MSH which is leading to melanogenesis. Melanogenesis is a process of production of melanin pigments which causes darkness of skin. Excess production of MSH also effects appetite and sexual arousal. Apply tretinoin cream 0.04% once daily for 30mins and wash off. Take multivitamins,irons and
calcium regularly. If your darkness of skin doesnot improve than consult gynaecologist.