The information should not be construed as dictating an exclusive course of treatment or procedure to be followed. Accurate dating of pregnancy is important to improve outcomes and is a research and public health imperative. As soon as data from the last menstrual period, the first accurate ultrasound examination, or both are obtained, the gestational age and the estimated due date EDD should be determined, discussed with the patient, and documented clearly in the medical record. Subsequent changes to the EDD should be reserved for rare circumstances, discussed with the patient, and documented clearly in the medical record.
When determined from the methods outlined in this document for estimating the due date, gestational age at delivery represents the best obstetric estimate for the purpose of clinical care and should be recorded on the birth certificate. For the purposes of research and surveillance, the best obstetric estimate, rather than estimates based on the last menstrual period 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 make the following recommendations regarding the method for estimating gestational age and due date:. An accurately assigned EDD early in prenatal care is among the most important results of evaluation and history taking.
This information is vital for timing of appropriate obstetric care; scheduling and interpretation of certain antepartum tests; determining the appropriateness of fetal growth; and designing interventions to prevent preterm births, postterm births, and related morbidities. Appropriately performed obstetric ultrasonography has been shown to accurately determine fetal gestational age 1. 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.
Women's Health Care Physicians
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.
- Ultrasound dates or LMP dates- which are more accurate?? in Your Pregnancy | Forum | Huggies!
- Methods for Estimating the Due Date - ACOG;
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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.
This information is for your general information and use only and is not intended to be used as medical advice and should not be used to diagnose, treat, cure or prevent any medical condition, nor should it be used for therapeutic purposes. The information is not a substitute for independent professional advice and should not be used as an alternative to professional health care. If you have a particular medical problem, please consult a healthcare professional. Access trusted, quality health information and advice Visit healthdirect.
Access quality information from pregnancy planning through to early parenthood Visit Pregnancy, Birth and Baby. Access information to help you navigate the aged care system Visit My Aged Care. A great place to start for support and services Visit Carer Gateway. General health Pregnancy and parenting Aged care Caring for someone. Dating scans are used to confirm how many weeks pregnant you are and your expected due date. Why would I have a dating scan? How is a dating scan performed? What preparation do I need to do for a dating scan? Check with your ultrasound clinic for any preparation you need to do prior to the scan.
The scan will take 5—10 minutes to perform. What will I learn from a dating scan?
Why would I have a dating scan?
At a dating scan you will also be able to: Australian Government Department of Health Guidelines for the use of ultrasound in the management of obstetric conditions. Opens in a new window. Hang in there- the last few weeks are always the toughest aren't they.
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Michelle, I wrote you a reply lastnight telling you I would ask at my Dr's appointment this morning. I dont know where it went?! Surely it wasn't deleted by the mods?
how accurate is a dating scan?
No swearing or anything in it! I did ask and he said to go by the EDD at your 12 week scan because they find that these are the most accurate. Apparently all babies grow at the same rate until the 12 week mark. So now he has changed my date too! Only by 3 days, but as I said to him, at the moment 3 days feels like an eternity to me! Hope you are travelling well.
how accurate is a dating scan? - Pregnancy: Tips, Questions and Information - Essential Baby
Thanks Jo, I did see your post this morning, I think I may have even replied, I haven't checked to see if it still there? I am confusing myself a little though because last night I posted it in two different places because no one seemed to be responding and I was bored! Anyway, as I have said previously I think deep down I am now thinking a lot about my 12 week ultrasound date but I have always said I would go with the later date.
So what is the date you are going off now? Our dates are close aren't they? Post deleted by administrator. My due date was calculated using both my LMP and a dating scan at 11 weeks. The sonographer took into account the date of my LMP adjusting for a 32 day cycle aswell as the size of bub.