Marginal Cord Insertion

So after my 20 week scan the doctor mentioned that I have marginal insertion of the umbilical cord, meaning that the cord is closer to the outer edge of the placenta rather than the middle. I have been reading things online but I am wondering if anyone on here has any experience to share? The doctor didn't seem overly concerned, but she is sending me for two additional ultrasounds...one at 28 weeks and one at 36. I am terrified that I am going to lose our little girl. I would love to know if anyone out there has experienced this and had a positive outcome. Thanks!