Early Pregnancy: Embryo Size & Heartbeat at 5 Weeks 5 Days

Question
I am 34 years old and this is my second pregnancy - my first pregnancy, four months ago, was a blighted pregnancy.  I have no children.  The first day of my last period was November 19th.  

My first sonogram (on January 4th) indicated that I was 5 weeks and 5 days pregnant - though counting from the first day of my last menstrual period I should have been 6 weeks and 4 days.  A heartbeat was detected (beating at a normal rate) and the size of the embryo was 0.24 cm.  My understanding is that a heartbeat is generally not detected until the 6th or 7th week, yet the size of the embryo is smaller than expected.  Does this mean the embryo is not developing properly?

Answer
As long as a heartbeat was seen and the sonogram measured it to be 5-6 weeks gestation, all appears promising. A sonogram at that stage of pregnancy is very inaccurate in confirming gestational age. You will have another sonogram at 12 weeks and again at 20 weeks (by LMP). At that time, the sonogram will give you an accurate determination of how far pregnant you are. For now, the sonogram merely confirmed that you have a viable, growing fetus. Good Luck to you.