Sometimes, there’s not much you can do to prevent stretch marks; you’re more likely to get them if they’re in your family history. Moreover, they may be more noticeable in people with darker skin. Rapid stretching of the skin is a risk factor, too (and you can’t really control the growth of your abdomen during pregnancy!).
But the best way to prevent stretch marks during pregnancy is to take good care of your skin: keep it well-hydrated by drinking plenty of water and eating a nutrient-rich diet, moisturize regularly and promote its elasticity with a product made with cocoa butter and exercise to foster the production of collagen, which makes skin stronger.