7 years before my delivery now also my stomach...

Symptomes and management of pregnancy stretch marks 
Pregnancy stretch marks are among the commonest manifistation of skin changes that happen during pregnancy, its caused by hormonal changes that lead to melanin deposition in the skin of the abdominal wall especially in the mid line in whats is called linea nigra, these marks will fade over time but some marks will remain spotted for life, the use of Hydroquinon cream twice daily for a duration of 3-6 months will help in regaining of the normal skin color.
Investigations 
Physical exam is the only invesetigations required 
causes 

• Pregnancy changes 
• Melanin deposition 
• skin redunduncy 

Our advice 
You are adviced to have a well balanced diet rich in minerals and vitamins, avoid smoking and have regular exercise