The only sure-fire way to prevent stretch marks would be to not get pregnant and never gain a large amount of weight. Both of those situations cause the rapid stretching of the skin that causes the marks.
If you plan on having children, there are some things you can try to prevent stretch marks, but it’s almost impossible to not develop any. During your first trimester start moisturizing the areas where stretch marks are most likely to develop — your belly, lower back, breasts, and hips. As for weight, keep your increase to 25 to 35 pounds to not overstretch your skin.
In your second trimester, if you still start seeing red lines, you can reduce their future appearance by acting now. Mederma Stretch Marks Therapy is safe to use in the second trimester, and it has been clinically shown to significantly minimize scarring. You have to apply it daily, though, and it will take a couple of weeks to show improvement.
After the baby is delivered, you want to firm your skin. There are products like Mustela Maternity Body Firming Gel that can do so.
Once you start to see stretch marks, that’s time to see our aestheticians if you really want to decrease their appearance.