Early Pregnancy Dating Scan Discrepancy: Is a 2-Week Difference Concerning?

Question
I am 38, have one child (age 2) and LMP was 10/8/05.  
I had my dating u/s this past Tues and it measured only 5 weeks 3
days vs 7 weeks 3 days. The concern by the doctors is that because
I knew when I ovulated I I used ovulation predictor kit), that it isn't
encouraging. Can they be wrong?  There was a sac, embryo and
heartbeat - Help!

Answer
If your last period started on October 8, you probably ovulated on October 21 and could have conceived if you had sex on october 20,21,22, or 23. A sonogram taken on November 23 should have shown a 6 week 3 days gestation. You could, of course, have conceived a bit later than you thought even if you used an ovultion prfedctor kit. In addition, a sonogram  this early in pregnancy is not accurate. Repeat the sonogram at 20 weeks for a more accurate computation of how far pregnant you are.