Question 1

my dr told me they do not add 2 weeks on the dating ultrasound. what does that mean?

Accepted Answer

Dates: a pregnancy id 40 weeks from the first day of the last period.  if your ultrasound gives the exact fetal age it is 2 weeks less than the age by dates.  So if you are 8 weeks pregnant the US in that case would say 6 weeks.  Some give the figure by dates some by fetal age ask which.

Question 2

had to dating ultrasound before 12 weeks are they accurate to within a couple days?

Accepted Answer

OB Ultrasounds: Yes. The early ultrasounds in an pregnancy are very accurate for dating.

Question 3

if i ovulated 2 weeks later will a dating ultrasound show this? or will it show that i ovulated on the usual day 14 of cycle?

Accepted Answer

Probably: A sonogram done early will accurately date a pregnancy within about 5-7 days.  This will show if you ovulated and conceived if you trace it back.

Question 4

my dating ultrasound was not consistent with my lmp. it dated me a week further than i should be. what could be the cause of this?

Accepted Answer

LMP dating vs US: Both methods have some error.  Us dating is most accurate between 8 and 13 weeks using the crown rump length of the fetus.

1 week difference is not a big deal at this stage.  Making sure interval growth is appropriate at your doctor checkups and the fetal anatomy ultrasound is what we all want to see.

Question 5

i have a question about a dating ultrasound? how accurate are they ? the dating based on my lmp and the date it puts me at are 10 days apart

Accepted Answer

1st trimester: If your dating ultrasound is in the 1st trimester, most doctors, if the ultrasound is off by &gt; 5 days of lmp, will use the ultrasound as has more accuracy.  Hope that helps your question!

Question 6

what do dating ultrasounds date? conception, lmp, or due date?

Accepted Answer

All : All if those can calculated after obtaining the gestational age.

Question 7

had first dating ultrasound at  14 weeks. edd feb 9, could my edd be off, could my due date b feb 25. seeing if may30 sex did it ?

Accepted Answer

Due dates: A 14 week scan is plus or minus 10 days or so.  Confirm with your OB, not the ultrasound tech is using first for the due day.  Due dates are for safety with regards to when its safe to deliver and when we need to delivery.  It is a best estimate only.  IF there is more than one possible father, you will need to get paternity testing.  Anymore only IVF patients have exact conception dates.

Question 8

i read that a dating ultrasound dates back to the date of conception. i.e. mine was 7w/50 and done on 4/24.  did i conceive around 3/1?

Accepted Answer

Due date: Use a reverse due date calculator for free online and this will be easy for you to find out. Simply type in your due date and the conception date will be calculated for you.

Question 9

if labor/delivery occurs after your due date, did conception occur later than suspected from the dating ultrasound?

Accepted Answer

Some variability: Us dating between 8-13 weeks is the most accurate  to within +/- 3-4 days. It is possible the dating by last menses may be incorrect as well, especially if menses are variable.

Although most women deliver around 40 weeks, not every delivery happens at 40 weeks.  Some are a couple of weeks early, others late.

Please discuss any questions with your doctor.

Question 10

if you ovulate later than the normal 14 days after lmp, would the dating ultrasound this and would it affect your due date?

Accepted Answer

Yes: Estimated due dates are just that - estimates.  1st trimester dating ultrasounds are based entirely on size measurements, regardless of lmp/ovulattion.  One measurement  is the "crown rump length" and another is the average size of the gestational sac.  If you conceived later, your ultrasound should measure smaller than the expected dates based on LMP and your due date would be later.

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Doctor answers about:

Dating ultrasound

A member asked:

My dr told me they do not add 2 weeks on the dating ultrasound. what does that mean?

A member asked:

Had to dating ultrasound before 12 weeks are they accurate to within a couple days?

A member asked:

If i ovulated 2 weeks later will a dating ultrasound show this? or will it show that i ovulated on the usual day 14 of cycle?

A member asked:

My dating ultrasound was not consistent with my lmp. it dated me a week further than i should be. what could be the cause of this?

A member asked:

I have a question about a dating ultrasound? how accurate are they ? the dating based on my lmp and the date it puts me at are 10 days apart

A member asked:

What do dating ultrasounds date? conception, lmp, or due date?

A member asked:

Had first dating ultrasound at 14 weeks. edd feb 9, could my edd be off, could my due date b feb 25. seeing if may30 sex did it ?

A member asked:

I read that a dating ultrasound dates back to the date of conception. i.e. mine was 7w/50 and done on 4/24. did i conceive around 3/1?

A member asked:

If labor/delivery occurs after your due date, did conception occur later than suspected from the dating ultrasound?

A member asked:

If you ovulate later than the normal 14 days after lmp, would the dating ultrasound this and would it affect your due date?

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