i had an ultrasound that said i was 13weeks 6 days, giving me a due date of 19th april, i had 1 today and it said i am 21 weeks 0 days giving me a due date of 14th april, which 1 would you say is most reliable?
2007-12-03 05:34:42 · 7 answers · asked by Anonymous in Pregnancy & Parenting ➔ Pregnancy
The first ultrasound will be most accurate. Ultrasound dating is more accurate earlier in pregnancy. We all start at about the same size, but we grow at different rates later in pregnancy.
"Many fetal measurements can be used to determine gestational age. Early in pregnancy (1st trimester), fetuses of the same gestational age all are nearly identical in size. At this time in pregnancy, there is very little difference in size between those fetuses who ultrimately will be large, average size, or small. As pregnancy continues, these genetic and constitutional differences in size become more important clinically. It is not possible, for example to separate a 20 week fetus who is large from a 21 week fetus of normal size, or a 22 week fetus who is small for its age. All three will measure as though they were 21 weeks.....The accuracy of ultrasound in predicting gestational age gets worse as the pregnancy advances. By 20 weeks, ultrasound is accurate only to within plus or minus two weeks, and by the third trimester, its accuracy falls to plus or minus 3 weeks."
http://www.obgyn.ufl.edu/obgyn101/Ultrasound/2nd%20and%203rd%20Trimester%20Ultrasound%20Scanning.htm
2007-12-03 08:00:46 · answer #1 · answered by Lissacal 7 · 0⤊ 0⤋
My first ultrasound said i was due on the 12th January and my 20 week scan says the 2nd. Thats a 10 day difference. So yes they can be wrong or out a few weeks. And yes, count the date from the start of the woman's last period. Which is usually 12-16 days before conception. Making the 7 week old technically only 5 weeks. Or she may have had an affair?
2016-04-07 05:54:22 · answer #2 · answered by Anonymous · 0⤊ 0⤋
An ultrasound technician told me that ultrasounds are most reliable within the first 10 weeks, after that genetics take over and its very approximate because of the genes affecting fetal development. I did the same thing my 1st pregnancy, but they always went with my 6 week ultrasound because it was the most reliable. In the end, it was right on schedule with the due date.
2007-12-03 05:42:19 · answer #3 · answered by Sweetness 6 · 2⤊ 0⤋
My first due date was dec 29. but since the sono was 10 days off from my last menstration cycle they just noted it. now my due date is dec 19. I have just figured out she will come when she wants to. you cant put an exact date on something like this.
2007-12-03 05:42:55 · answer #4 · answered by Anonymous · 1⤊ 0⤋
The most recent one....I've had 5 differnt due dates! First it was feb 28th..then march 25th...then march 19th...back to march 25th... then to march 17th and then they finally stuck with March 14th when I had my ultrasound...lol its crazy so who knows. But you can go anywhere from 2 weeks before your due date to two weeks after.
2007-12-03 05:41:22 · answer #5 · answered by Anonymous · 0⤊ 1⤋
The most recent one. Its normal for them to vary by a few days. It doesnt change anything- generally you never give birth on your due date anyway, its just a ball park figure.
2007-12-03 05:38:49 · answer #6 · answered by amosunknown 7 · 1⤊ 1⤋
My ob/gyn said to go with the earliest U/S as far as due date..My first said I was due Feb 4,My second said,January 28th..I had my son Feb.1st..Congrats
2007-12-03 05:45:03 · answer #7 · answered by Brat25 4 · 1⤊ 0⤋