QuestionMy baby is due on april 20th 2008, on my first prenatal appointment my doctor did and internal ultrasound and told me i was 6 weeks pregnant, with my due dat being 04/20 that means i concieved somewhere around the 29th of july. I slept with someone other than my boyfriend on the 28th of june. is there any way possible my ultrasound is off by a whole month...? this has really been eating away at me. I am desperate to know that my boyfriend is the father. PLEASE HELP ME!!!
AnswerDear Lauren,
At 6 weeks, transvaginal ultrasound is very accurate in dating pregnancies. If that ultrasound was done around 8/27 (which I'll assume), and it was determined that you were approximately 6 weeks, 1 day along and due on 4/20, conception would have occurred on approximately 7/29 (based on a 28 day cycle). If conception would have occurred on 6/28, your gestational age would have been determined to be 10 weeks 4 days at that ultrasound. There is a HUGE difference in size/development between 6 weeks and 10 weeks. For instance, at 6 weeks the fetus will measure about 0.45 cm; at 10 weeks the measurement is approximately 3.1 cm - nearly 7 times the size!
So, an ultrasound being off by a few days is one thing and very possible. But 4 weeks is just too much of a size differential to be missed that early on in a pregnancy. I truly think you can rest easy. :-)
I hope this has helped you and answered your question. I wish you well.
Brenda
