my ultrasound was 14 days off why did they change due date?

Question

i had a ultrasound from last menstrual at 15 weeks 5 days after ultrasound it was 13 weeks 5 days . my last menstrual was accurate so why they change due date if it was only 2 weeks off.

Answer 1

The ultrasound is a more accurate way to see how far you are. When they go by your lmp it is a guessing game. The ultrasounds gets the week and day - that is why they sometimes change the due date.

Answer 2

They go by the first day of your last period, but those charts are set up for 28 day cycles, which normally (on average) would mean that you ovulated 14 days from the 1st day. Now that is not always the case. I had my first ultrasound at 9.5 weeks. The charge shows I was 10.5 weeks & due date of 2/11 but the size of the fetus says I'm 9.5 weeks and sets the due date @ 2/19. Big difference. I've read several articles that say that both your ovulation and the ultrasounds can be off, give or take 5 days. Some also said that the ultrasounds solely calculates on the size of the fetus, so what if you've got a small baby?

Answer 3

the due dates by ultrasound are estimates derived from various parameters used to measure the baby, depending on how far you are in your pregnancy. rule of thumb is that the most accurate estimates are from ultrasound examinations done during the 1st 3 months, with a larger margin of error towards the last few months of pregnancy. the ultrasound reported due date however, will be based on ultrasound measurements and not on your last menstrual period.

if you are sure about your last menstrual period, and if your cycle is fairly regular, the ultrasound estimated date of delivery would likely be fairly near your calculated due date. as a rule, it should not be off by more than two weeks (plus or minus).

we usually regard repeated (meaning in more than one ultrasound examination) discrepancies of than two weeks in either direction, as either due to incorrect (menstrual) dates or an indication of a small (or large) for gestational age fetus, which in turn might indicate a potential problem, and which might need a closer study.

Answer 4

My due date changed 3 times, then went back to the original date. Besides...wehn you are 4 weeks...you are really only 2.

Answer 5

ultra sound is more accurate . they use the last mestral peroid date as an estimate . most women ovulate in mid cycle so for those that do, going by your peroid is accurate , but for those of us who dont ovulate like the others our dates may be off and corrected by ultra sound .
i wouldnt worry about it at all . just means you got pregnant 2 weeks later then the norm .
enjoy your pregnancy , and congrats !!!!!!

Answer 6

i am not understanding your question but usually doctors give something called an estimated due date(EDD) based on calculations from your last period when i saw my doctor he gave my EDD as 31st july but when i had my ultrasound it gave my EDD as 4th august ( my son was born on the 4th August) ( it is said that they begin calculations from 2 weeks before you concieve which means they calculate from two weeks before you are actually pregnant strange huh)

Answer 7

hey yeahh the same thing happen to me they said mine was going to be the 26 og august..but now its the 18..but now there not actually sure b.c. they said it actually seems like shes going to come a lot sooner if i don't drink a lot of water..

Answer 8

They are going by the size of the baby & his/her development. It's more accurate.