Marginal placenta previa at 20 weeks

Hello ladies! My s/o and I went to our 20 week ultrasound yesterday and found out baby is doing good! The only issue that he brought up, was that the edge of our baby girls placenta is located right next to my cervix. He didn't seem too concerned about it but at the same time, he wants to check again at 30 weeks to be sure it won't be a problem. Have any of you ladies experienced marginal placenta previa and the placenta moving? Should we get a second opinion?