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.

[Emily_MHManager]

Hi everyone -

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[AnnieBrooke]

Hi Blah, you would be due no later than August 21 if the sex on November 28 had produced the pregnancy.  Get tested for STDs and forget about it.  

[Blahblah16]

Can some one help I had sex with some one nov 28 but use the pull out method smh but I had sex with my bd everyday including that day my due date is sept 11 2016 my bf is the father right?? Im not sure when my last period is

[AnnieBrooke]

Although in the old format, it's blue and says "Post Question."  

[hbic16]

Annie please help

[AnnieBrooke]

Hi, hbic16, you're adding to an 800-post thread that began in June, 2012.  Due to the way these long threads work, it is possible nobody will ever see your question.  Why don't you post it as its own question?  Go to the top of the page, click on DNA/Paternity, and then look for "ask question" or "post question" and click on it.

[AnnieBrooke]

I just checked, it's red, and it says "Ask a question."  At the top of the page.

[hbic16]

My last period was Dec 23,2015,and I had sex with my ex bf that day and the condom popped.We broke up then I hooked up with a future ex a week later my ob said I conceived jan 17 who's the daddy?

[hbic16]

How to ask a question on here?

[AnnieBrooke]

December 20.

[Lungi88]

I was not 42 the scan also confirmed that If gave birth 29 th Aug it was 38 and not 40

[AnnieBrooke]

If you had the baby at 40 weeks on September 12 (no doctor told you that you were 42 weeks, right?) the conception date where 40 weeks = September 12 is December 20.  

[AnnieBrooke]

Hi, Lungi, second guy for definitely sure.

[Lungi88]

My edd was 29 august (38weeks) in which 40 weeks is 12 September (actual birth date of my child) first guy 05 DEC second guy 16 dec

[AnnieBrooke]

Sorry, two weeks *after* Day 1.  It is more helpful to work from a due date, though.  Did the doctor give you an EDD (estimated due date)?  If so, would you say what it is, and also the dates of the sex with the guys?

[AnnieBrooke]

Hi, Lungi, it does sound like the second guy has a chance to be the father if he had sex with you two weeks before Day 1.  Did the doctor give you a due date?  If so, when did you have sex with each guy (calendar days)?

[Lungi88]

Hi the second person we were safe that's y I Dont even consider him in ma head but my problem is when I count back using the scan the 06 the becomes day 1 on the scan which disqualifies the guy i slept with on the 5th because the first 2 weeks u not actually pregnant I'm so confused cud the second guy be the father? Is the a chance that something happened to the condom and we did not see

[AnnieBrooke]

Hi, Lungi, what do you mean "dating scan starts counting 06 DEC"?  Do you mean that you got a scan, and you think it is in a good range of weeks for using it to date the pregnancy, and if you count back the number of weeks and days all the way to 0, December 6 is day 0?

Was December 5 the only time you had sex with that particular guy?  If so, I assume you are saying you had sex in December with another person?

[Lungi88]

Hi if I had sex 05 dec and dating scan starts counting 06 DEC does this mean the guy I slept with on the 5th is not the father?

[AnnieBrooke]

Hi, Joshie / Vicky, could you post as its own question?  Especially with the new format MedHelp is beginning to use, it is very hard to answer questions in a lot of detail when they are on the end of an 800-post thread.  Just copy the question and hit the button to "ask a question."  That way, you will get an email when anyone answers instead of having to search out the thread.

Also want to mention that if an ultrasound has been done, the count of "weeks pregnant" the tech will mention (or the doctor, nurse or midwife) does not start with the presumed conception date, but with the first day of the presumed last period, conception happening after that about 2 weeks.  So if you were told 5-6 weeks "pregnant" by a medical person, that would mean 3-4 weeks since presumed conception.  This would particularly apply if you had an ultrasound.

[Vicky000]

Hello please help, trying to determine who the father of my child is, the sexual encounters occurred three weeks apart. The first encounter was right at the time when I was either ovulating or close to ovulation. The second encounter took place three weeks later. When I went for the scan the size of the foetus indicated roughly 5-6 weeks. The first encounter was 28 jan and the second 22 Feb. When do you start calculating conception from. The 5 weeks seems to little for the January guy. Please advise

[Joshie0]

Hi please assist. Recently discovered in expecting. Took a blood test that revealed I was six to seven weeks pregnant. Went for a scan with my gp and it said five to six weeks. I has sex with one guy on 28 January 2016 and the other on 22 February 2016. I initial thought I was pregnant with the Jan guy but early home pregnancy tests came back negative. I then thought I had my period in mid Feb but it lasted for just two days which was strange for me. Im thus uncertain to count the Feb period as one since it may have been just bleeding for other reasons as even the flow was too light compared to normal. Please advise who is the likely candidate. Oh further my last clear period was in January, think the first day was around 12 or 13 Jan. This would have meant I was close to ovulation when I had sex in January. I was actually hoping to conceive then as I love this man although we had recently broken up. What do you think? Im having sleepless nights from stress.

[AnnieBrooke]

If she had an ultrasound on February 16 and the embryo was seen after it not being seen on the 12th, it rather sounds like there was a difference between ultrasound machines (some machines have higher resolution than others).  This would mean nothing in terms of trying to date the pregnancy.  It would just mean one machine could see the pregnancy and the other could not.

If this was the same machine, same technician and same doctor, she might have been in her 5th week on February 16.  As you know, the GA dates like "5th week" mean two weeks less since conception, so let's say she was somewhere around three to three and a half weeks or so since conception on February 16.  That points to conception in the late January.  Sperm from your last sexual encounter (if it was January 17) could last long enough in her system to extend into that time period.

I think you really need to have a heart-to-heart talk with this girl about whether or not she only had a sexual encounter with someone else on January 6.  Talking to someone on the Internet is not going to answer this question.  If she had sex with the other guy after you left (I assume you're saying you left on the 17th and weren't back after that again until she knew she was pregnant) then a DNA test is called for.  If she never again had sex with him after the 6th, I don't think there is much chance at all that the baby was from him.

[boontew]

Hi Annie, I was with her the whole time from Jan6 to Jan 17. How is the odd of conceive this baby having sex on 18?
Thanks

[AnnieBrooke]

I guess the only issue would be if she had sex with the other guy later than January 6, such as after you were gone.  But so far, everything you say tends to rule out the guy January 6.

[AnnieBrooke]

In the FAQs enclosed with Plan B, it says there is a 1 in 8 chance it will not work.  Your girlfriend should not have been taking it randomly, it is not good for her, she should only take it perhaps once every couple of years.  (It is not intended to replace birth control pills.)  In short, Plan B is not a totally infallible medication.