I started using this during the second trimester of pregnancy. I already had numerous old, white stretch marks from puberty. While I did not develop any new stretch marks during pregnancy, Mederma did not noticeably change the appearance of my old stretch marks, so I am somewhat disappointed. I know the product information states that it does not work as well on old stretch marks, but it did not work at *all* on them. I applied the product as directed. I do think it might have helped to prevent me from developing new stretch marks during pregnancy, and I would use it during future pregnancies and would probably recommend it to friends who are worried about developing stretch marks during pregnancy.