Are ultrasound conception dates accurate?

[tina6146]

I discovered I was pregnant unexpectedly, and went to have an ultrasound on May 23rd. Due to having wavering periods, I never really keep track, and therefore I don't know when my last period was. I can give an "estimate" but I really don't know because I never keep track. (Plus I have always been told that because of metabolic issues, and PCOS that it would be very hard for me to get pregnant).
Anyway, not exactly proud of this, but I was with 2 different men in a two week time period. One I didn't use protection with on Saturday April 7th (we have been very good friends for years, and it just happened on a night out drinking/dancing) and the other man I only went out with a few times, and when we slept together the following week (on Saturday April 14th), the condom broke. I didn't think anything of it, because I am almost 38, and this has never happened to me before.
So, my question is, when I went to have my ultrasound, the sonographer did 2 measurements for the conception date: one was 6 weeks and 3 days, and the other one (just to be sure) was 6 weeks 5 days. So, we split the difference and said 6 weeks 4 days. This would make my conception date April 7th, which is the exact night I was with the first man.
Do you think there's a big chance that the 2nd man could potentially be the father? I am hoping the first man is indeed the father, because we have been friends for years, and it would be alot easier to handle. The second man, however, I don't even speak to anymore. I would hate for it to be the second man.
Any advice on people that have gone through this? I guess I just want some confirmation that these ultrasound dates are accurate. The ultrasound tech was amazing, and I feel like she really knew what she was doing, but I just want to make sure that these results couldn't be a whole 7-8 days off.

[AnnieBrooke]

Well, you sure didn't get pregnant in early February.  If you only had sex with Guy A on February 1 and 5 and then not after that (and don't forget, it was well before your period, which did come), then he is not the dad.

[xoxoJulie]

He did a Transvagianl ultrsound on me when I was 5 weeks and thats the due date he gave me.. So Guy B?  

[AnnieBrooke]

How did your ob-gyn get to the due date of November 23, was it by an ultrasound?  If so, guy B is the dad.

[xoxoJulie]

hi annie my name is Julie and I will be 10 weeks tomorrow (April 28th) My OBGYN determined that my due date is November 23rd, 2015. my problem is which it may not even be a problem BUT I had sex with Guy A on Feb. 1st and 5th and i am pretty sure he didnt come in me well then i had my period on Feb. 16th-20th and I had sex with Guy B on Feb. 19th, 20th, 26th and also the 2nd of March and Guy B did *** in me all 4 times.. which one is the father

[AnnieBrooke]

Hi, Mark.  Here is the problem.  Unless she had an ultrasound in her 7th or 8th week (and this means 7th or 8th from her first day of her last period, not from the presumed date of conception), it is really not very useful to try to figure out a conception date from an ultrasound scan.  All babies begin as one cell, and they split into 2 on the next day, and 4 on the next day after that, and so on at a relatively standard rate, but by the time week 8 or 9 comes around, some embryos will begin to grow or develop more quickly or more slowly than the average.  So by the time she is '4 months 2 weeks' (I assume this means 18 weeks) from her first day of her last period, the margin for error when using an ultrasound to try to figure out when conception was can be as much as a week or two either direction.  

In short, only a DNA test will tell you who the father is.  It is too late to tell from an ultrasound.

If she had an ultrasound in her 7th week, and if they told her a due date at that time which was computed only from the embryo's size and developmental markers, you could use it to try to make this kind of assessment.  But not one done in her 4th month.

I don't know the law in Kenya, but in the United States I believe it would be possible to see an attorney and force a DNA test for paternity, once the baby is born.  It might be worth you speaking to a lawyer to see if you have that right.

[marktwo]

hello Annie.am mark from kenya, my girlfriend is pregnant for 5M and 1W now.  My girlfriend and I are living away from each other due to school stuf. My girlfriend just confessed to me that she cheated on me with her ex boyfi sex a few weeks before I came to visit her back home. I was with her on the 10th of Nov 2014 to 15th Nov 2014 and made love all those days.  After I  was gone, again she had sex with her ex 1 week after i left for school.  I now want to  know whose baby is this.  when school closed and i was home for holidays she experienced blood discharge fro her vagina so I took her for  vaginal scan (because had a spot bleeding) tht was on the 24th March 2015 and as per the ultra sound scan it was 4 Months and 2weeks, the doc told us that we have to sub 1 week from the scanning date to get the date she will get the bby.  That said, am getting convinced that this might be my daughter but she claims its her ex ,am very worried and scared because she now wants to move in with her ex claiming she is doing the right thing by living me. she has even rejected the doctors date of concieving that was 21st Aug this yr..she claims she will be conceiving on 11th Aug n not 21st as per the scan results.Please help me on this.  I am really banking on your reply.