Sorry I don't know anything about cord insertion.

If you are worried the doc is being is too positive, you could always ask more specific questions at your next appointment. Maybe come prepared with a list of questions like "Does this condition increase my or baby's risks in any way? If so, how? How frequently does this occur in normal healthy pregnancies," etc.

I did find an old ask the expert response (to a question regarding pre-e & infant loss) where the expert said they weren't aware of any connection between pre-e and marginal cord insertion. http://www.preeclampsia.org/forum/viewtopic.php?f=19&t=117&p=7706

Good luck, please keep us posted if you learn anything else at your next appointment.

We just had our anatomy scan and while baby is measuring perfectly and fluid looks good... they discovered that I have a marginal insertion of the cord. He said it's not a big deal and that we'll be watching me closely anyways so it won't change our plans... but I really didn't need anything to be more nervous about. I'm worried that he wouldn't really tell me if it was a concern because he knows I'm already terrified. Does anyone have any experience with this or knowledge on it?