Fetal size and heart rate

[adnt]

I went to the OB this morning to have an ultrasound to confirm pregnancy.  They did see an embryo and detected a heart beat.  However, they told me by my dates (meaning the date that I last had my period) I should be 6.5 weeks pregnant and that I was only measuring 5 weeks and 5 days.  The heart rate was fine if I am 5 weeks and 5 days but if I am 6.5 weeks pregnant then it is too low and there is a high risk of miscarriage.  Can anyone tell me what the chances are that I may have ovulated late and that I am not as far a long as I might think or if this situation means miscarriage for sure.  The only things I can find on the internet talk about low fetal heart rate seem like there is a 100% chance of miscarriage.  

[Zarabikhan]

Hello Elaine

I have question regarding few prenatal test I have went through.Hope you can help me.
My history: I gave birth to a clubfeet baby girl.I had a normal delivery.Baby was born almost at the end of nine month without any complications.At the age of 5 months my daughter had 3 episodes of pneumonia.In the third episode she was diagnoised with trachemalacia and zenker's diverticulum.At age 1.5 yrs she died.I am pregnat for the second time,my gynaec is been very careful this time she is making me get  all the prenatal tests.
Can you please suggest some more prenatal  tests.
One more thing I got my Free beta HCG and PAPP A test by CLIA serum.The values I got were 15.0 ng/ml and 3.20 mIU/ml respectively .My NT measurement was 0.7 mm.
I am 11.6 weeks pregnant according to my LMP(19/09/09).But the ultrasound showed me 12.4 weeks pregnant.Since we went through so much for the first baby.I am bit worried about this one.Can you help me  by telling if the values that have come for HCG and Papp A is in normal range or not.

Thank you

[Elaine Brown, MD]

HI!
The chances that your dates are "off" or that the ultrasound dates are "off" is very HIGH.  Once we see a heart beat on the ultrasound there is a very good chance that the pregnancy will continue.  In my practice we even see lots of babies with slow heart rates that do fine.  If the ultrasound probe is twisted a tiny bit, the measurement can change by several days.  Even if the probe is exact, there is still an error of 3-4 days is the measurement.  The chance that your ovulation was delayed by 2-3 days is pretty good. I'll bet (hope so!) your baby is fine!
Good luck!
Dr B