Doctor insights on:
Is Your Lmp Or Ultrasound Most Accurate
If LMP and 12 week ultrasound correlate, would the u/s be considered more accurate since the LMP is known? Or is there still 1 week margin of error?
An ultraound, also known as a sonogram, is a painless and relatively inexpensive imaging test that utilizes sound waves instead of ionizing radiation. There are no side effects. Ultrasound can give us two-dimensional, and in some applications three-dimensional, images of structures and organs in virtually any part of the body. In addition to diagnostic uses, such as evaluating abnormalities in the abdomen, pelvis, and breast, ultrasounds are commonly used to guide needle and catheter placement in a variety of surgical ...Read more
Usually close. : Studies have shown that up to 20 wks gestation, ultrasound can vary by as much as 1.2 wks. Others have shown a 2 wk variaton between 18 to 28 wks, and 3 wk variation at greater than 28 wks. In a normal developing fetus, variations are usually secondary to the experience and expertise of the technologist, position of the fetus, and the accuracy of the measurements. ...Read more
Pregnant?: I assume you are pregnant. Early transvaginal ultrasound is very accurate and giving a proper gestational age for you pregnancy. From that age a due date is given and an "lmp" date is given even though you may not have actually had a menstrual cycle at that time. ...Read moreSee 1 more doctor answer
If last LMP is not known would a ultrasound measure sac in early pregnancy to match gestational age ?
Yes: An early transvaginal ultrasound can accurately estimate the gestational age within a couple of days. In the first trimester, there is very little biologic variation in size. If the embryo is present, the "crown-rump length" is routinely measured and used to determine the gestational age. Also, the mean diameter of the gestational sac gives a reasonable estimate of age. ...Read moreSee 1 more doctor answer
Best on earlier u/s: Ultrasounds use composite data obtained during the exam to determine an EDD (estimated date of delivery). This date will also have a +/- number of days giving an accuracy range. First trimester ultrasounds are accurate to within about a week, second trimesters estimates are accurate within about 2 weeks, and third trimester scans about 3 weeks. ...Read more
Ultrasound dating: The first. First trimester ultrasound is accurate within 5-7 days. 2nd trimester ultrasound has accuracy of +/_ 2 weeks. Lmp dating also assumes a 28 day cycle. There is no test that can date conception more accurately than a 1 week window. Due date is based on lmp unless us off by more than 1 week 1st trimester or 2 weeks in 2nd. ...Read more
What changes a due date? And why is the first trimester ultrasound more accurate than the second trimester ultrasound?
Ultrasound dating.: First trimester ultrasound is by far the most accurate in determining the precise due date (+/- 3-7 days, depending on exactly when it is performed). Second trimester sonograms are less accurate but still helpful in pegging down the due date within +/-7-12 days. Third trimester scans are not very accurate in dating the pregnancy, as growth varies (+/- 14-21 days). Menstrual dating is not very good. ...Read more
Which is more accurate. An ultrasound at 5 weeks 5 days or 8 weeks 3 days? What would be the margin of error for the one most accurate?
Both: I'm not sure where you are going. Both dates are very accurate for dating a fetus. The margin of error is about a week ...Read more
Ultrasound dating: First trimester ultrasound is accurate within 5-7 days. 2nd trimester ultrasound has accuracy of +/_ 2 weeks. Lmp dating also assumes a 28 day cycle. There is no test that can date conception more accurately than a 1 week window. Due date is based on lmp unless us off by more than 1 week 1st trimester or 2 weeks in 2nd. ...Read moreSee 1 more doctor answer
Is the age shown on an ultrasound measured from LMP or conception? The US said 5w1d. If this is from LMP, conception would be after I got a pos. test
From LMP but..: ...If the sonographic dating was obtained from measuring the "mean gestational sac size", its margin error may be wide and it may be inaccurate. If it was determined from the average of 3 measurements of a "crown rump length" by a certified experienced sonographer, it is more reliable and precise. A repeat scan in a few weeks may be valuable. ...Read more
6-8 weeks: Ultrasound dating is most accurate early in the pregnancy using the crown-rump length (crl) of the small fetus. The measurement can be done starting around 6 weeks. While crl can be used for dating until 12 weeks, it is most accurate during 6-8 weeks when the accepted error is only about 3 days from actual date. ...Read moreSee 1 more doctor answer
Which gestational age is more accurate, LMP based or ultrasound one? By LMP i am 27weeks and 4 days.ultrasound says 28 weeks
Ultrasound is better: Ultrasound is certainly a better estimator of gestational age than lmp in the first trimester and the first half of the pregnancy. The lmp is often off. Many women will experience some spotting at 4 weeks and consider that a menstrual period. The ultrasound can also evaluate the fetus and placenta and detect potential problems early. ...Read more
Embryo transfer: Embryo transfer would be the ultimate gold standard for gestation age.The number of days since conception of the transferred embryo (3-5 days) would be known so the precise time of conception would be available so the estimated due date could be more precisely estimated. ...Read more
What is the margin of error for an abdominal ultrasound in the first trimester. Around 11 weeks. Would vaginal be more accurate?
My due date is aug 7 according to 11 week ultrasound and 24 week ultrasound. What is the accuracy of these ultrasounds and conception day?
+/- 1 week: The accuracy of an 11 week ultrasound should be +/- 1 week. ...Read more
Is an abdominal us at 11wks accurate for dating a pregnancy? What is the range of accuracy? Possible to be 4 weeks off? Ex measure 11wks but be 15wks?
No should not be: An 11 week us should be accurate within 1 week either way a the most and usually more accurate than that. ...Read more
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