Accuracy of Ultrasound

Question

I have a question in regards to the accuracy of ultrasounds. I am told my due date was Nov 4. I know my lmp was January 18. My doctor told me I may be wrong that my lmp should of been January 28. I am asking this because I had sex January 28 and was not on my period. I also had sex Feb 1, and Feb 5 and 6. I am needing to know how accurate they are, because I had sex with 2 different partners. Please help. If I go by my lmp i would of conceived around the 1st. If I go by the ultrasound I would of conceived around the 5 and 6. Thank you for any help you can give me.

shell0209 · Answer

The same thing happened to me, I had regular periods before I got pregnant my lmp was nov 2nd and on my u/s they have nov 13 they said some people might have regular monthly periods but might ovulate at a later date so they told me the u/s date is more accurate if done before the 12th week. Good luck with everything.

superchoc · Answer

after ovulation, you may have a late/early embryo implanting. also going to add to being a few days out

alaysha · Answer

Because they assume during ultrasounds that you have a regular cycle (28) days if you have a linger cycle then you most likely ovulated later since ovulation is usually about 2 weeks before your period is due.

jewels2011 · Answer

yes I am going to have a paternity test done. But how can an ultrasound say my lmp was at a time I knew I was not having my period? I was very regular on my periods every 28 to 29 days. For my lmp, it would make the time between periods 39 days. Just wondering.

alaysha · Answer

Ultrasound are only accurate in the first 13 weeks. After that babies develop at their own rate and measurements can be a couple weeks off. Even in early pregnancy it can be up to a week off. The only thing you can do is get a paternity test once the baby is born.

superchoc · Answer

i had the one due date given by LMP so i KNEW when i got pregnant etc. at 35 weeks they changed it from the 15th to the 22nd so i was given an extra week. dont know why they left it as late to tell me as they could have told me at the 12 week scan as baby measured a week smaller

kerriekab · Answer

The ultrasounds are the most accurate way of dating the pregnancy. The dr will go by the lmp but you could have ovulated early or late so the ultrasound gives them the most accurate date and the dr will take that date and use that for future dates and due dates.