All information I have read has indicated that sonograms are highly unstable. They are printed on thermographic paper and will eventually turn completely black. There is no way to preserve the actual sonogram. But, you can make a copy at the copy store (white paper is archival quality) or scan it into your computer and print it out. Or, take the sonogram to a Kodak Picture Maker and print it out on photo paper. You may want to take the opportunity to enlarge it.
We are working on some frames for scrapbooking sonograms. If you would like to be notified when these are ready please email me at nickwilberg @ hotmail.com