Early Pregnancy Ultrasound: Understanding Gestational Sac & Yolk Sac at 5 Weeks

Question
Dear Doctor,
My Stats:

Age:  43
Children:  0 (did not start trying to have children until 10 mos ago)
LMP:  11/11/05

I went in for vaginal U/S on 12/21/05.  I am not sure of the counting but I believe it is 5 weeks 6 days.  Is the next day 5 weeks 7 days or 6 weeks?

In any case, they saw the gestational sac and the yolk sac.  They did not mention anything else.  Should they have seen the heartbeat at this time?  I thought it definitely was there at 6 weeks.  What about an embryo/fetus?  

My HCG levels are good.  I believe on 12/21 it was in the 20,000 range.  In any case they are rising.

I am terrified of miscarriage due to my age.  I was also told I could not conceive because of high FSH.  At what point will things start looking good and I can think this is actually going to happen.  

Answer
If you are pregnant and your last period started on November 11, then on December 21 you were only 5 weeks 5 days pregnant (from the first day of your last period). Prior to 6 weeks, we only see (on sonogram) an empty gestational sac. After 6 weeks, we see a fetus and a fetal heartbeat. I would repeat the sonogram in a few weeks. You are correct. Five weeks 7 days is really Six weeks. Your HCG level appears good. Good Luck with the rest of the pregnancy.