How accurate is dating ultrasound

Nov 3, An ultrasound exam is a procedure that uses high-frequency sound How accurate are ultrasounds in determining the conception date to.
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Because I'm high risk history of 8 miscarriages and severe pelvic inflammatory disease I've had 6 ultrasounds. My first one, turns out I was 4w3d, we couldn't see anything. My second one was 5w4d, I had a sac but no fetal pole, it dated me earlier than I could have been.

How is an ultrasound performed?

Number 3 through 6 have all dated the baby consistantly 7w through 12w5d. I'm done with ultrasounds now, I've just hit my second trimester!!! It looks like by the last period date you gave, you are about 9 weeks.

How can I know when I conceived?

A dating ultrasound now should be fine, you should be far enough along to see a fetal pole, and maybe even a heartbeat even if you ovulated a week or 2 late. Thanks for responses - it sounds like ultrasounds are somewhat accurate within a week or so I am not the type to worry about what day I just let it happen Originally Posted by Mom2Adam. My mw said before 10 weeks is accurate for dating.

Not due in December, but I have not had a period "lining up" with my due date. Ultrasound confirmed that I was right. I think they are supposed to be fairly accurate but mine was a week off.


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It was a week behind my date and I gave birth the day before my date and I don't go early so I think my date was way more accurate. I had an ultrasound at 9w2d by my conception day calculation because it didn't match up with my last period my cycles are long and it was bang on. The baby was measuring just a tad over an inch and looking just like a 9 week old should.

I too have hear that they are very accurate in the week range. Before an after that there is too much individual variation.

Methods for Estimating the Due Date - ACOG

Early ultrasounds are so accurate because embryos grow at very much the same rate. Once you get past past the embryonic stage and into the fetal stage, the beans start growing at different rates.

Methods for Estimating the Due Date

I'd been charting, not temps, just CM, sex, and periods to keep track. No having to lie about lmp.

How accurate is the Estimated Due Date by ultrasound?

Then during physical exam, she said my uterus was measuring more like 16 weeks what!!! After losing the last preg. It was a very confusing hour and I'm just now coming out of the fog! A consistent and exacting approach to accurate dating is also a research and public health imperative because of the influence of dating on investigational protocols and vital statistics. This Committee Opinion outlines a standardized approach to estimate gestational age and the anticipated due date.

However, there is great usefulness in having a single, uniform standard within and between institutions that have access to high-quality ultrasonography as most, if not all, U. Accordingly, in creating recommendations and the associated summary table, single-point cutoffs were chosen based on expert review. Because this practice assumes a regular menstrual cycle of 28 days, with ovulation occurring on the 14th day after the beginning of the menstrual cycle, this practice does not account for inaccurate recall of the LMP, irregularities in cycle length, or variability in the timing of ovulation.

It has been reported that approximately one half of women accurately recall their LMP 2—4. Accurate determination of gestational age can positively affect pregnancy outcomes. For instance, one study found a reduction in the need for postterm inductions in a group of women randomized to receive routine first-trimester ultrasonography compared with women who received only second-trimester ultrasonography 5.

A Cochrane review concluded that ultrasonography can reduce the need for postterm induction and lead to earlier detection of multiple gestations 6. Because decisions to change the EDD significantly affect pregnancy management, their implications should be discussed with patients and recorded in the medical record.

Measurements of the CRL are more accurate the earlier in the first trimester that ultrasonography is performed 11, 15— The measurement used for dating should be the mean of three discrete CRL measurements when possible and should be obtained in a true midsagittal plane, with the genital tubercle and fetal spine longitudinally in view and the maximum length from cranium to caudal rump measured as a straight line 8, Mean sac diameter measurements are not recommended for estimating the due date. Dating changes for smaller discrepancies are appropriate based on how early in the first trimester the ultrasound examination was performed and clinical assessment of the reliability of the LMP date Table 1.

For instance, the EDD for a pregnancy that resulted from in vitro fertilization should be assigned using the age of the embryo and the date of transfer. For example, for a day-5 embryo, the EDD would be days from the embryo replacement date. Likewise, the EDD for a day-3 embryo would be days from the embryo replacement date. Using a single ultrasound examination in the second trimester to assist in determining the gestational age enables simultaneous fetal anatomic evaluation.

With rare exception, if a first-trimester ultrasound examination was performed, especially one consistent with LMP dating, gestational age should not be adjusted based on a second-trimester ultrasound examination. Ultrasonography dating in the second trimester typically is based on regression formulas that incorporate variables such as.

What types of ultrasound are there?

Other biometric variables, such as additional long bones and the transverse cerebellar diameter, also can play a role. Date changes for smaller discrepancies 10—14 days are appropriate based on how early in this second-trimester range the ultrasound examination was performed and on clinician assessment of LMP reliability. Because of the risk of redating a small fetus that may be growth restricted, management decisions based on third-trimester ultrasonography alone are especially problematic; therefore, decisions need to be guided by careful consideration of the entire clinical picture and may require close surveillance, including repeat ultrasonography, to ensure appropriate interval growth.

The best available data support adjusting the EDD of a pregnancy if the first ultrasonography in the pregnancy is performed in the third trimester and suggests a discrepancy in gestational dating of more than 21 days. As soon as data from the LMP, the first accurate ultrasound examination, or both are obtained, the gestational age and the EDD should be determined, discussed with the patient, and documented clearly in the medical record.

For the purposes of research and surveillance, the best obstetric estimate, rather than estimates based on the LMP alone, should be used as the measure for gestational age. The American College of Obstetricians and Gynecologists, the American Institute of Ultrasound in Medicine, and the Society for Maternal—Fetal Medicine recognize the advantages of a single dating paradigm being used within and between institutions that provide obstetric care. Table 1 provides guidelines for estimating the due date based on ultrasonography and the LMP in pregnancy, and provides single-point cutoffs and ranges based on available evidence and expert opinion.

No part of this publication may be reproduced, stored in a retrieval system, posted on the Internet, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher. Methods for estimating the due date.

Ultrasound: Sonogram

American College of Obstetricians and Gynecologists. Women's Health Care Physicians. Recommendations The American College of Obstetricians and Gynecologists, the American Institute of Ultrasound in Medicine, and the Society for Maternal—Fetal Medicine make the following recommendations regarding the method for estimating gestational age and due date: As soon as data from the last menstrual period LMP , the first accurate ultrasound examination, or both are obtained, the gestational age and the EDD should be determined, discussed with the patient, and documented clearly in the medical record.

Introduction An accurately assigned EDD early in prenatal care is among the most important results of evaluation and history taking.


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Clinical Considerations in the Second Trimester Using a single ultrasound examination in the second trimester to assist in determining the gestational age enables simultaneous fetal anatomic evaluation. Ultrasonography dating in the second trimester typically is based on regression formulas that incorporate variables such as the biparietal diameter and head circumference measured in transverse section of the head at the level of the thalami and cavum septi pellucidi; the cerebellar hemispheres should not be visible in this scanning plane the femur length measured with full length of the bone perpendicular to the ultrasound beam, excluding the distal femoral epiphysis the abdominal circumference measured in symmetrical, transverse round section at the skin line, with visualization of the vertebrae and in a plane with visualization of the stomach, umbilical vein, and portal sinus 8 Other biometric variables, such as additional long bones and the transverse cerebellar diameter, also can play a role.

Conclusion Accurate dating of pregnancy is important to improve outcomes and is a research and public health imperative. Fetal Imaging Workshop Invited Participants. A comparison of recalled date of last menstrual period with prospectively recorded dates.