You're probably ok and should check with your OB/GYN for reassurance.
Based on what I know and have read radiation exposure is not good for pregnant women or their fetuses, but if a fetus is accidentally exposed to a small amount of radiation (from a chest x-ray for example), it is extremely unlikely that any damage will result. You did the right thing by informing the technician and wearing a shield...plus, the x-ray was of your chest not abdomen.
Also, I did a brief search on this and found the following --it's not your exact case (since you had a chest x-ray, but it's close enough)--
Dental x-rays in pregnancy
by Christine Hill
Having only just found out that I am pregnant. I am concerned that just after my last period I visited the dentist and they took a small X-ray of my teeth. Would this have an effect on my baby?
Dawn
Dear Dawn
There’s absolutely no need for you to worry. X-ray machines today give tiny doses of radiation and are directed at a highly localised area. You receive more if you sit in the sun for 10 minutes.
Good luck with your pregnancy.
Christine Hill
Antenatal Expert
[This message has been edited by BoardManager (edited 08-12-2003).]