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Are ultrasound conception dates accurate?
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.
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Avatar universal
Thank you so much for the reply.  I honestly don't know when ultrasound was done.  I imagine it was done around the typical time (12-18w?) and her date hasn't changed.  We have been talking off and on about this and I recommended a DNA test.  She has been reluctant until recently to get this.  But, still hasn't done anything yet.  Its hard for me to move with my life worrying about this. I don't want to get into another relationship with someone that I may care about and have the "its your baby" thrown in.  I suppose my question is that based on EDD of 2/11/16 and the times we had sex, there is a possibility that I could be the father correct?  According to online calculators it puts the ovulation around 5/21.
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Also, she did a ovulation test 5/26 which was positive.  I found were a positive ovulation test could mean positive pregnancy as well.  Im so confused.  If there is a decent chance based on EDD of 2/11, then I would like to press her a little harder to get the noninvasive DNA test now.
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sorry to keep adding to the discussion thread.  I feel the EDD is accurate because it was confirmed by a mutual friend and probably done around mid July. This is going to sound odd, but the reason I am accurate with my dates, is that we were actually trying to get pregnant since January and we were keeping track of her cycle.  In fact, I have in my records that she had some spotting 5/9, then a period 5/14-20.  The previous periods that I have were 2/13-17, 3/13-18, and 4/8-15. Negative preg test 4/22.

Do you think based on this there is a chance I could be the father?  I realize its mostly speculation and only a DNA test will exclude me.  Are the noninvasive tests that swab my check and match it against fetal cells in her blood reliable?  I'll shut up now and await your thoughts.
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134578 tn?1483549754
Hi, sadyear, the site is changing its display style, and when the new version comes up, it is very hard for me to fish up comments off the bottom of an 800+ post thread.  Would you mind very much beginning a new question?  If you do, MedHelp also alerts you to any answers.

When you begin a new post, could you just write out the issue briefly, and say when her periods were, when you had sex in May, what the ultrasound said and when it might have been done, and when she says she had sex with the other guy?  I could try to puzzle it out from there.  Unfortunately, not knowing when in her pregnancy the ultrasound was done (that provided the estimated due date) is going to make calculating things rather iffy.  But if you are certain the date has never changed, that helps.  

Why were you trying to have a baby with someone who lied to you a lot?  You do know, I assume, that prenatal DNA testing costs $1600 or more?
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new thread started
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134578 tn?1483549754
Thanks, I see it and will respond.   -- Annie
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Dear annie. well my wife was cheating on me and is now living with the other man. The problem is we had protected sex 16 nov. She went for an ultra sound 12 dec and the ultra sound said that the conception date is 16 nov. By the she has been sleeping allot with the other man. I want to know if it is possible that the baby can be mine.
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134578 tn?1483549754
Hi, Dirkestan, if an ultrasound gave evidence that a doctor told your wife meant conception was November 16, it is possible for either of you to be the father, since condoms are not 100% effective.  I assume she was told on December 12 that she was about 5 weeks 5 days gestational age (dated from first day of last period) or 3 weeks 5 days since conception, and the doctor (not your wife or you by yourself) came up with the assertion that she conceived on November 16?  Even though your chances (having used protection) are less than the man with whom she is now living (if she did not use protection with him), it would be a good idea to do a DNA test to rule you out for sure, .Of course, if you both used protection, then a DNA test is the only thing that will tell you for sure.
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134578 tn?1483549754
Dirkestan, I might have not been very clear.

1.  IF the date for conception is right, then you do have a chance to be the dad, because condoms only have about an 80% effectiveness rate.

2.  The way to know if the date for conception is correct is to analyze where it came from.  If the doctor looked at the ultrasound and offered this specific date, and said it is the conception date, that suggests accuracy.  Did he say she was 5 weeks 5 days 'pregnant'?

If the doctor gave some information and then your wife figured out the conception date on her own, (or you did), then that is not as useful because it could be based on misunderstanding what the doctor did say.
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Dear Annie,
I was dating another man the month of August and moved states September 1st and found myself in another relationship. September 1st - 4th I had what I thought to be a "period". September 27th I took a pregnancy test and had a positive result. However, I had an ultrasound with a midwife November 4th and she stated I was 11 weeks along with a due date on May 24th, which made it impossible for me to have had a period the 1st of September (according to her). With my period having been on September 1st my due date should have been June 7th NOT May 24th, but at my first ultrasound having a due date of June 7th would have put me at 9 weeks along NOT 11. If you could give me your input on whether you believe I conceived in August or September that would be great, I'm pretty torn up about this and researching different prenatal paternity test options. Is there any way my midwife is wrong about her dates? Thank you.
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134578 tn?1483549754
Sorry, did you say your first ultrasound gave you a due date of June 7 or May 24?
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The ultrasound gave me a due date of May 24th. Thanks for responding.
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134578 tn?1483549754
At what point in the pregnancy was the ultrasound that gave you a due date of May 24, was that at 11 weeks?
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134578 tn?1483549754
I was just a little thrown by you saying "but at my first ultrasound having a due date of June 7th would have put me at 9 weeks along NOT 11."  
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134578 tn?1483549754
I guess I'm also a bit thrown by this part  " I had an ultrasound with a midwife November 4th and she stated I was 11 weeks along with a due date on May 24th."  If someone had an ultrasound on November 4 that said she was 11 weeks 0 days, she would be due on May 28, I think.
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Yes, my midwife told me that I was 11 weeks along on November 4th. On that day she calculated that my due date was May 24th. Even though I told her that i had a lmp date of September 1st.
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I hope that made sense!!
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134578 tn?1483549754
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
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134578 tn?1483549754
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.
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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.
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134578 tn?1483549754
Is that why you remember so clearly that you had a period September 1 - 4?  
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134578 tn?1483549754
Also, did you have ANY sex in the last week of August, protected or not?  If so, was the protection condoms?
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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.
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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.

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And condoms were my choice of contraception the last week of August.
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134578 tn?1483549754
Well, you are not in a good spot to know who the father is without a DNA test, unfortunately.  
1.  Condoms are only 80% effective
2.  Sperm can live in the woman's reproductive tract 5 or 6 days
3.  The midwife gave you a weeks date (if she said 11 weeks 0 days) and an estimated due date on a certain date, and the dates were not consistent each other
4.  Your period did not correspond to your ovulation according to the midwife [is your period always exactly a certain number of days from the previous one without fail?]
5.  You had sex with two men close enough together that if there was condom failure they both could have had living sperm in your body at the same time
6.  Your earliest ultrasound wasn't early enough to pinpoint when you got pregnant with the precision you need, and any you get from now on could have a larger margin for error

I would not hesitate to use either Ravgen or the DDC, if you test with both men.  I would recommend Ravgen over the DDC only because I have never heard a credible complaint about them.  I have only heard one credible complaint about the DDC, and out of the huge number of tests they must do, that is not a lot.  In your shoes I would not hesitate to test using either lab.  
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Thank you for your response, you've been a huge help!!!
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Annie,

My gf and I had sex on Jan 14 and Jan 15 a lot of times. She found out she is pregnant on Feb16 and ultrasould put her 6w1d pregnant which saying she conceived on Jan 18. But when she had her second ultrasound on Mar 10, ultrasound put her 10w3d pregnant and conceived on Jan 11. She told me that she ate Plan B on the Jan15 evening.
She admitted that she had sex with another guy, didn't tell me when, but it is before Jan6 as I was still with her that day. I left her for work on Jan17 again, not sure if she was with the guy again or not.
What is the odd of the baby being mine if she did had sex with the other guy on Jan5? I am hoping the baby is mine and I can forgive what she did, if the baby is not mine, I will ask the guy to responsible for it for the good of the baby. Btw, her LMP was on Dec15 but only last for 2 days. She had irregular cycle as she took Plan B few times in a month. Should we go with her LMP or ultrasound? Is it possible that the Plan B on 15 did not take effect as we had several times of sex on the 14 itself? How accurate is the ultrasound on 6 and 10 weeks?

Thanks
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134578 tn?1483549754
Ultrasounds are more accurate at 6 weeks for this purpose than at 10 weeks, and the way she is taking Plan B, she would certainly have irregular cycles that could not be used to count forward from to determine a conception date.  By 10 weeks, an ultrasound could be several days off for dating purposes.  Sex prior to January 6 would probably be too early to produce a baby.  In your shoes I would operate on the assumption that the baby is yours, but would do a DNA test once the baby arrives just to put the question to rest forever.  
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Thank you for your response
She went to the clinic on Feb 12, the doctor told her that she had miscarriage as nothing shown up on the ultrasound. I was thinking this is because she told that her LMP was on Dec 15 which put her 2w more. She waited few more days then had another one on Feb 16 only then it can be seen in the us. Was it too early to have an ultrasound scan on Feb12. But there is only 4 days gap though. Does it make more on dating the coception?
I am confident that the baby is mine but I was wondering how the plan B failed. Is it because she took it too many times in a month? How the plan B work in delaying the ovulation? What makes her cycle longer than normal cycle she had before?
Thanks again.
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134578 tn?1483549754
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.  
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134578 tn?1483549754
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.
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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
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134578 tn?1483549754
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.
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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.
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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
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134578 tn?1483549754
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.



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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?
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134578 tn?1483549754
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?
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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
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134578 tn?1483549754
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)?
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134578 tn?1483549754
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?
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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
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134578 tn?1483549754
Hi, Lungi, second guy for definitely sure.
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134578 tn?1483549754
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.  
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I was not 42 the scan also confirmed that If gave birth 29 th Aug it was 38 and not 40
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134578 tn?1483549754
December 20.
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How to ask a question on here?
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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?
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Annie please help
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134578 tn?1483549754
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.
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134578 tn?1483549754
I just checked, it's red, and it says "Ask a question."  At the top of the page.
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134578 tn?1483549754
Although in the old format, it's blue and says "Post Question."  
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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
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134578 tn?1483549754
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.  
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707563 tn?1455827280
Hi everyone -

We are closing this thread. If you'd like to ask your own question, please click on the button at the top of the page that says "Post a Question" (on mobile, at the bottom of the screen, tap "Ask a new question").

Thanks!

Emily
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