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# Calculating conception date

I have been reading a lot of forums and other websites since our first ultrasound and find myself more confused than ever when trying to determine our conception date.  The ultrasound determined that the baby was 7 weeks 2 days old on January 6.  From what I understand to calculate the conception date we subtract 2 weeks from the 7 weeks 2 days which gives us 5 weeks 2 day or 37 days.  So then I subtract 37 days from January 6 and I would get a conception date of November 30th.  The thing I don’t get is that the first day of her last cycle was November 2nd.  Is it possible that the conception date could be 28 days after the first day of her cycle?  Also when we looked at how long her cycle normally was on average it was 31 days.  Also so that you understand why I’m asking we only had sex on November 11, 13, 14, and 15 and December 6, 8, and 9 because of work travel.  Is it possible someone else is the father or did I calculate the conception date wrong – if I don’t subtract the 2 weeks I think it makes sense because the date would be December 16th.   Any help you could provide me would be great and thank you.
Ben
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Hi!
When the ultrasound and the LMP are so different, we usually discard the LMP.  These dates are VERY often confusing.  It is also important to realize that there can be an error of up to 3-7 days in the ultrasound measurement.  When I use my wheel, December 6 looks pretty suspicious to me---and I'll bet that you're the man!
Good luck and Congratulations!
Dr B
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Elaine,

Thank you for your input.  What would your thoughts be if she had intercourse on November 24th.  Is it normal that the date can come so late?

Thank you,
Ben
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im having a problem regarding my pregnancy. my husband refuses to acknowledge the child my carrying now as his.
my husband works abroad. he came home last dec 24. my last period was dec 7.  I had a pregnancy test last jan 14 and it was positive. My husband was a bit surprised why that fast and started to have doubts about it.
i had my first ultrasound last jan 22. the result was 5 weeks and 6 days.My husband was surprised and started to insult me of who the father is. This is really difficult. This is really affecting my pregnancy and the marriage. I had to repeat the ultrasound two weeks after. I had it last Feb 6.Im 8 weeks pregnant base on it.
And so my husband wouldn,t believe me that I didnt cheat on him. And he has decided not to acknowledge this child. Im really sad right now. I dont know how long this marriage will last. I dont know how things will go in the next days, weeks and months.

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Charee- have your doctor explain that when the ultra sound says 5w6d that's the gestation age. It would actually but your conception date dec 24th. You said your lmp was 12/7. So and 14 days to that... (12/24) and that's your conception date. If you have a regular cycle (28-32) days the you would ovulated around 10-16 days after the first day of your last period. Good luck to you and your family
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I had sex 2 guys same week . My lmp 11/13/2010, I has sex with the guy A nov. 21 guy B nov 24-28 . I used a condom with guy A but I think I'm nervous bc of the guilt . They say my conception day is nov 27 I'm nervous.... So is it just nerves or should I be worried?
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Im in the same situation. I was split up wit my bf.and was wit guyA Only 1 time protected tho on jan1 and then i got bak wit my bf 2days later which we were always unprotected bt my duedate is 0ct9.and i just had an ultrasound july8 and it says my GA=gestational Age is 26wks5days.i mean that adds directly to jan1.bt my 0bgyn said not2worry bc i had2conceive between the dates jan.9-jan15.and GA=meaning fetus age counting from LMP.BT THE PROBELM IS I CANT REMEMBR THE EXACT DAY 0F MY LMP.BT IT WAS IN DEC. CAN SUMONE PLZ HELP EXPLAIN IT TO ME.I BEEN STRESSN SO MUCH OVR THIS.PLZ?
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Omg same situation!! Me nd my bf split up and I had protected sex twice with guy A which was around 3/5 or 3/6 and also 3/11. I got back with my bf and had unprotected sex once, between the dates 3/14-3/16, I dnt really remember which one of these dates. My first day of my lmp was on the 2/27 or 2/28. I went to the doc. Nd got my first ultrasound nd they said my due date was nov.30 so I got pregnant march 2nd, then I got referred to another OB nd my dd changed to dec.10 which says I got pregnant march 12 :( I'm really confused nd having doubts to who could b the dad.could someone plz explain what's goingg on or give me your opinion plzzzzz????
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