QuestionDoctor,
I got pregnant after a frozen IVF cycle. I am 10 weeks pregnant - and things have been good so far EXCEPT one issue.
When I went for my first ultrasound at about 6 weeks - we saw that the CRL length showed the baby at 5weeks 4 days and as per the transfer date I was supposed to be 6 weeks pregnant. So I was lagging by about 3 days.
After that I went again at 7 weeks and the CRL length showed I was pregnant at 6 weeks 3 days - a lag of about 4 days.
I went again at 8 weeks and the CRL length showed I was pregnant at 7 weeks 2 days - a lag of 5 days.
Finally I went at 9 weeks and the CRL length showed I was 8 weeks 1 days pregnant - a lag of 6 days.
So every week I go the lag has been increasing by a day - now it is about 6 days behind when I compare the CRL lenght and the transfer date calculation. (I am sure I am counting the transfer date accurately).
Everything else is normal. The latest 2 heartbeats (at 7 and 8 weeks pregnancy) have been around 172 bpm; and so that is fine.
My question is:
Every week the lag between the pregnancy age becaues of the CRL measurement and the transfer date keeps increasing by a day - and now I am about 6 days behind.
Is that a reason to worry?
What must be causing this? What can we do to find out more?
Please let me know since this has me worried now.
AnswerPrior to 14 weeks gestation, a sonogram is very inaccurate, as are crown-rump lengths. A sonogram taken at 14 weeks or 20 weeks is much more accurate as they measure biparietal diameter and abdominal circumference. The error in early sonograms is 3 weeks, while the error in a sonogram measurement between 14-22 weeks is only 14 days (+ or -). A lage of 2-6 days is insignificant. It does not mean that the baby is not growing. It is merely an error in the sonographic measurement. Don't worry.
