Ultrasound Accuracy in Early Pregnancy: Understanding Due Dates

Question
Hi, I wanted to know if you could help. My periods tend to be off a few days and my cycles are 30-33 days. On July 13 2009 I took an hpt and it said I was pregnant. I went for ultrasounds right away 6th 7th and 8th weeks all saying my due date was March 24 2010. Based on this I was told I concieved around the 3Oth of June give or take. How off can an ultrasound be? Is it possible I concieved around June 13th? Thanks

Answer
Hi Sabrina,

First trimester ultrasounds are accurate +/- 3 days. Your ultrasounds point to ovulation occurring late June/early July.  

You did not conceive June 13; that is too far from the dates that the ultrasounds are giving.

Sincerely,

Dorothy H., LCCE