Expert: Dorothy H, LCCE - 11/4/2009

Question
I know this is long but thank you for taking time out to read it. When I went to my first u/s on 10/8/09, they told me I was 9w.3d. I went yesterday 11/3/09 and they did another u/s and said they were wrong. They said I was 10w.5days and changed my due date from 5/10/10 to 5/27/10. They asked me when I thought I got pregnant and I said 9/3/09, just because the next day i felt "different" but I really don't know. My cycles are irregular, now i am lost because i really don't know when i got pregnant and I'm kinda scared that my doc could be really off on my dates like she was the first time. I am going to speak with her about this but i just needed another opinion. I did have unprocted sex on 9/3/09 and protected sex (with a condom, and he even pulled out when he was reaching that point)around 9/8 or 9/9. I heard that early ultrasounds were the most accurate so how could they have been so far off the first time. On my first u/s I saw the yolk sac and I saw a flicker (heartbeat) it looked like it was outside the baby's body. This time, the baby looked more human, the heart looked like it was inside the body and I saw the hands moving. The doc did say that when I thought I got pregnant matched up perfectly with my u/s findings. Just wanted to see what you thought. Thank you.

Answer
You raise a lot of good questions - if you conceived on 9/3, that would put your due date at the 2nd u/s estimate of 5/27/10.   If your due date was 5/10/10, you would have conceived mid-August. If you did not have sex at all mid-August, then it looks like the 2nd u/s is the one that is accurate.

Yes, generally an earlier u/s is more accurate, but these are both 1st trimester ultrasounds, and neither one should be off by 17 days.  Your questions are valid and you need to be asking your doctor these questions, and if your doctor is not able to answer them satisfactorily, ask herif you could talk to an ultrasound tech, who could show you both u/s  and explain why s/he feels the first one isn't accurate.  Something just isn't adding up here.  

I hope you are able to get answers soon.