QUESTION: My Lmp was 5/27/12 i had my first transvaginal ultrasound an july 23 i was 8w1d from lmp and the ultrasound measured the fetus at 7w3d then i had an ultrasound 13w2d from lmp and abdominal ultrasound measured fetus at 12w3days .. The cenception calenders say i concieved june 9/10..... Is ultrasound more accurate or the calulators? Did i concieve around june 6th? Or the 9/10th?

ANSWER: The ultrasound is pretty accurate when it comes to due dates, when they do them in the first trimester. They actually measure the baby's size, but also look at what parts of the baby are developed, and almost all babies develop at the same rate in the first trimester, so they can know with pretty good precision when you conceived. According to their calculations you conceived on June 16th. When they say 7 weeks 3 days they add two weeks to get to what they think is your LMP. But they mean that the baby is actually 5 weeks and 3 days old from conception. If your periods are generally far apart, then it would make sense that you would ovulate later in your cycle, and get pregnant later in your cycle. That would be a reason why the calculations look wrong.
Calculating from the LMP is actually the least accurate way to calculate. The most accurate way is to calculate from when you ovulated, if you know the date. The next best way is the ultrasound, if it's done in the first few weeks of pregnancy. Calculating from the LMP is only accurate if you have regular periods that are always 28 days apart.
Best of luck,

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QUESTION: But at my first ultrasound i knew my LMP which was may 27, 2012 and on my ultrasound vist july 23, 2012 i was 8w1d from my LMP and the ultrasound tech said the baby is measuring 7w3d. When she gave me the ultrasound report and images on it it say 8w1d not 7w3d ... Therefore isnt 7w3d the fetal age and therefor i dont need to subtract the 2 weeks??  And my due date has stayed the same of 3/3/13. So would i count back 7w3d for estimated conception date and not subtracting 2 weeks since my pregnancy is still being dated from my lmp? Im confused can you please clarify.

It is extremely unlikely that your LMP is only 6 days away from your conception date.
If your ultrasound measured you at 7w3d but she wrote on your report 8w1d, then you'd have to clarify with her why she went with your LMP dates instead of your ultrasound dates.
Usually they choose one or the other, and it seems in their case that they chose to use the due date based on your LMP.
I've never seen the days and weeks of pregnancy counted from conception, only from the LMP or ultrasound calculations. (They can be calculated that way, but are never charted that way, in my experience.)
You'll have to ask your tech or doctor why there's a discrepancy.
Without seeing the notes in your chart I wouldn't be able to know that.
Again, if your cycles are long, then your ultrasound dates are probably more accurate.
Best of luck,


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