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.

[doomed23]

Yes I did have intercourse the last week of August but it was protected and yes that is exactly how/why I remember my period clearly started September 1st.

[doomed23]

I'm currently debating choosing ravgen over ddc. However I've read online that few people have recieved false positives and negatives from both labs which worries me. Im weighing the pros and cons of waiting until my baby is born to test paternity.

[AnnieBrooke]

Also, did you have ANY sex in the last week of August, protected or not?  If so, was the protection condoms?

[AnnieBrooke]

Is that why you remember so clearly that you had a period September 1 - 4?  

[doomed23]

I did not have unprotected sex with the significant other I had during August during the last week I was there, however I did have unprotected sex with the guy from the month of September multiple times from September 1st until the 7th.

[AnnieBrooke]

Anyway, if you had sex before coming to the United States as late as the last couple of days of August, and then had sex once arriving in the United States as early as, say, September 4 or 5, an 11th-week ultrasound will not help you decide who is the dad.  Sperm can live 5 or 6 days in your reproductive tract, and by week 12, most doctors doing ultrasounds for purposes of determining conception will say "give or take 7 days."  (By the time you are at 40 weeks, the margin for error will be +/- 3 weeks.)

If you didn't have sex with Mr. Home Country in the last week of August, and if you didn't start up with Mr. USA until perhaps the second or third week of September, you could speculate with perhaps some certainty that the baby came from Mr. USA.  But if you did have sex with both guys within only a few days or a week, you will need a DNA test.  Prenatal DNA tests are available from two good labs (that I know of) and several charlatan labs that will just waste your money.  If you want to go the prenatal route, try Ravgen or the DDC.  Both have affiliate labs all over the world, I believe.  The cost is about ten times higher than if you had a test after the baby is born, but especially if you test with both guys, you will get an answer.



Prenatal

[AnnieBrooke]

To clarify, I am wondering when the last time you had sex with Mr. Old Country was, and when the first time you had sex with Mr. Brave New World was.