Stretch marks are unwanted scars that appear on the skin due to sudden changes in body size, and this usually happens during pregnancy, rapid weight gain or loss, and puberty. Development of stretch marks is common among women during and after pregnancy. You might have fine lines mostly in the areas prone to fat accumulation like breast, hips, arms, abdomen, tummy and thighs.
Pregnancy stretch marks form as a natural result of the skin around the abdomen stretching out to accommodate a growing belly. The marks start out as red streaks and turn silvery over time. It is possible to prevent and reduce the appearance of stretch marks if you act early. Drink water to keep your body well hydrated. During pregnancy, your blood volume is increasing, and you are building a huge water sack for your baby to stay in. Your body has growing demand for hydration. Your skin also needs to be hydrated for optimal skin elasticity.
It is advisable to take 8-12 glasses of water each day and to consume enough Zinc. Zinc deficiency is one reason people are more likely to get stretch marks.  Zinc is a natural trace mineral and one of the most abundant in the body. Zinc is used in the production of collagen and also contains antioxidant properties. Zinc is found in foods like chicken, lamb, beef, eggs, nuts, legumes and whole grains.
Eat a balanced and nutritious diet that is rich in vitamins C and E, zinc, silica, and other nutrients to nourish your skin. Vitamin C, in particular, is essential for regenerating connective tissue. Expectant mothers often are advised to use castor oil to prevent stretch marks. Castor oil has been used for ages to prevent and reduce fine lines, wrinkles, spots, blemishes, and other skin problems. Here’s how you use it:

Castor oil(Stretch Marks)
Apply a thick layer of castor oil on your skin.
Wrap the area with plastic wrap or saran wrap
Apply heat with a heating pad or hot water bottle for at least 20 minutes
Repeat the process daily or several times a week  
If you wish to thin the oil, combine one tablespoon of castor oil with two tablespoons of sweet almond oil and then apply the mixture.