1.If she is pregnant this is called Linea nigra otherwise it is normal hyperpigmentation,due to increase in melanin hormone.
2. any use of contarceptives pills?
3. use Vit.E Lotion and vitamin C to reduce the darkening and keeping the veins healthy.
4. coca butter is very much useful in lightening the symptom.
welcome to healthcaremagic
This line black what you are complaining is normal during pregnancy and may last for long after. This is prominent sign of pregnancy There is nothing to worry and treatment in this regards