Accuracy of Early Ultrasound

[jobdaname]

I am a nurse and i have a few questions reguarding the accuracy of early ultrasound dating. My last period was November 17th, 2011. I had a positive pregnancy test on December 22nd, 2011. I went in for my first ultrasound on January 26st and measured at 9 wks 1 day. Everything seems to be right on track! I have been with my boyfriend since October 20th, 2011, i have never cheated on  him but i was with someone in early/ towards the middle of october and he was doubting paternity even though the ultrasound says i conceived around november 23rd. What are the chances that the baby may not be his?? Im now at 23 weeks and had one ultrasound at 16 wks where i measured 16.5 wks and another at 21 wks where i measured 22 wks 1 day. Is all this normal? i feel like i have never doubted him being the father but the more he talks i think is it possible for the ultrasound to be off that much? Any info is appreciated thank you!!

[Heather5]

I fully agree with AnnieBrooke. There's no doubt that the baby is your boyfriend's! based on the dates and the ultrasound, I'm 100% sure! Congratulations on your pregnancy!

[AnnieBrooke]

Your first ultrasound is the most reliable because babies grow at different rates.  Later ones can be as much as a week off.  But nothing would be so off that it would fill in the difference between October 20 and November 23.  This is especially true with a period November 17, and also because your first ultrasound is the one to rely on.  Your boyfriend is being paranoid, and shame on him for planting doubt.  It sounds like you are going to have to get ready for him to demand a DNA test.  What a jerk.