Calculate delivery due date , gestational age and other important dates during pregnancy using LMP, ultrasound dating, or date of conception (IVF) Ultrasound uses the size of the fetus to determine the gestational age (the time elapsed since the the first day of the last menstrual period). The accuracy of the ultrasound estimate of the gestational age varies according to the gestational age. Ultrasound measurement of the embryo or fetus in the first trimester (up to and including 13 6/7 weeks of gestation) is the most accurate method to establish or confirm gestational age .The Society of Obstetricians and Gynaecologists of Canada recommends the earliest ultrasound with a crown rump length equivalent to at least 7 weeks ( .
(Replaces Committee Opinion Number 611, October 2014) Committee on Obstetric Practice American Institute of Ultrasound in Medicine Society for Maternal-Fetal Medicine This Committee Opinion was developed by the American College of Obstetricians and Gynecologists’ Committee on Obstetric Practice, in collaboration with members Christian M.
Pettker, MD; James D. Goldberg, MD; and Yasser Y. El-Sayed, MD; the American Institute of Ultrasound in Medicine’s liaison member Joshua A. Copel, MD; and the Society for Maternal–Fetal Medicine. This document reflects emerging clinical and scientific advances as of the date issued and is subject to change. The information should not be construed as dictating an exclusive course of treatment or procedure to be followed. Methods for Estimating the Due Date ABSTRACT: 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.
A pregnancy without an ultrasound examination that confirms or revises the EDD before 22 0/7 weeks of gestational age should be considered suboptimally dated.
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. 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: • Ultrasound measurement of the embryo or fetus in the first trimester (up to and including 13 6/7 weeks of gestation) is the most accurate method to establish or confirm gestational age.
• If pregnancy resulted from assisted reproductive technology (ART), the ART-derived gestational age should be used to assign the estimated due date (EDD). 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. • 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.
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 LMP alone, should be used as the measure for gestational age.
• A pregnancy without an ultrasound examination that confirms or revises the EDD before 22 0/7 weeks of gestational age should be considered suboptimally dated. Introduction 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 (). 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. It is understood that within the ranges suggested by different studies, no perfect evidence exists to establish a single-point cutoff in the difference between clinical and ultrasonographic EDD to prompt changing a pregnancy’s 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.S.
obstetric facilities do). Accordingly, in creating recommendations and the associated summary table, single-point cutoffs were chosen based on expert review.
Background Traditionally, determining the first day of the LMP is the first step in establishing the EDD. By convention, the EDD is 280 days after the first day of the LMP. 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 (). In one study, 40% of the women randomized to receive first-trimester ultrasonography had their EDD adjusted because of a discrepancy of more than 5 days between ultrasound dating and LMP dating ().
Estimated due dates were adjusted in only 10% of the women in the control group who had ultrasonography in the second trimester, which suggests that first-trimester ultrasound examination can improve the accuracy of the EDD, even when the first day of the LMP is known.
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 (). Because decisions to change the EDD significantly affect pregnancy management, their implications should be discussed with patients and recorded in the medical record. Clinical Considerations in the First Trimester Ultrasound measurement of the embryo or fetus in the first trimester (up to and including 13 6/7 weeks of gestation) is the most accurate method to establish or confirm gestational age (3, 4, ).
Up to and including 13 6/7 weeks of gestation, gestational age assessment based on measurement of the crown–rump length (CRL) has an accuracy of ±5–7 days (). Measurements of the CRL are more accurate the earlier in the first trimester that ultrasonography is performed (11, ).
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, 11).
Mean sac diameter measurements are not recommended for estimating the due date. Beyond measurements of 84 mm (corresponding to approximately 14 0/7 weeks of gestation), the accuracy of the CRL to estimate gestational age decreases, and in these cases, other second-trimester biometric parameters (discussed in the following section) should be used for dating. If ultrasound dating before 14 0/7 weeks of gestation differs by more than 7 days from LMP dating, the EDD should be changed to correspond with the ultrasound dating.
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 (). For instance, before 9 0/7 weeks of gestation, a discrepancy of more than 5 days is an appropriate reason for changing the EDD.
If the patient is unsure of her LMP, dating should be based on ultrasound examination estimates (ideally obtained before or at 13 6/7 weeks of gestation), with the earliest ultrasound examination of a CRL measurement prioritized as the most reliable. If pregnancy resulted from ART, the ART-derived gestational age should be used to assign the EDD. 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 261 days from the embryo replacement date. Likewise, the EDD for a day-3 embryo would be 263 days from the embryo replacement date. 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.
However, the range of second-trimester gestational ages (14 0/7 weeks to 27 6/7 weeks of gestation) introduces greater variability and complexity, which can affect revision of LMP dating and assignment of a final EDD.
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 • 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.
Gestational age assessment by ultrasonography in the first part of the second trimester (between 14 0/7 weeks and 21 6/7 weeks of gestation, inclusive) is based on a composite of fetal biometric measurements and has an accuracy of ± 7–10 days ().
If dating by ultrasonography performed between 14 0/7 weeks and 15 6/7 weeks of gestation (inclusive) varies from LMP dating by more than 7 days, or if ultrasonography dating between 16 0/7 weeks and 21 6/7 weeks of gestation varies by more than 10 days, the EDD should be changed to correspond with the ultrasonography dating (Table 1). Between 22 0/7 weeks and 27 6/7 weeks of gestation, ultrasonography dating has an accuracy of ± 10–14 days (19). If ultrasonography dating between 22 0/7 weeks and 27 6/7 weeks of gestation (inclusive) varies by more than 14 days from LMP dating, the EDD should be changed to correspond with the ultrasonography dating (Table 1).
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. Of note, pregnancies without an ultrasound examination that confirms or revises the EDD before 22 0/7 weeks of gestational age should be considered suboptimally dated (see also Committee Opinion 688, Management of Suboptimally Dated Pregnancies ).
Clinical Considerations in the Third Trimester Gestational age assessment by ultrasonography in the third trimester (28 0/7 weeks of gestation and beyond) is the least reliable method, with an accuracy of ± 21–30 days (19, 20, ). 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.
Conclusion Accurate dating of pregnancy is important to improve outcomes and is a research and public health imperative. 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.
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 LMP alone, should be used as the measure for gestational age. A pregnancy without an ultrasound examination that confirms or revises the EDD before 22 0/7 weeks of gestational age should be considered suboptimally dated. 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. References • Reddy UM, Abuhamad AZ, Levine D, Saade GR. Fetal imaging: executive summary of a joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal–Fetal Medicine, American Institute of Ultrasound in Medicine, American College of Obstetricians and Gynecologists, American College of Radiology, Society for Pediatric Radiology, and Society of Radiologists in Ultrasound Fetal Imaging workshop.
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 Copyright May 2017 by the American College of Obstetricians and Gynecologists. All rights reserved. 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. Requests for authorization to make photocopies should be directed to Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400.
ISSN 1074-861X The American College of Obstetricians and Gynecologists 409 12th Street, SW, PO Box 96920, Washington, DC 20090-6920 Methods for estimating the due date. Committee Opinion No. 700. American College of Obstetricians and Gynecologists.
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best dating pregnancy by lmp vs ultrasound - Due Date Calculator: The Most Precise Conception Calculator
wikiHow is a wiki similar to Wikipedia, which means that many of our articles are written collaboratively. To create this article, 11 people, some anonymous, worked together to author and improve it over time. Together, they cited that can be found at the bottom of the article.
This article has also been viewed 35,720 times. The fetal ultrasound, or sonogram, has become a routine aspect of prenatal care for most pregnant women. High frequency sound waves are used to scan the expectant mother's abdomen and pelvic cavity, to create a picture of the fetus and placenta.
These routine exams are considered safe for mother and child, and it is in fact quite simple to get an ultrasound for pregnancy. Understand the importance of the ultrasound exam. The ultrasound exam is used to evaluate the fetus' growth and development, and to determine how the pregnancy is progressing. Two ultrasound exams are performed over the course of your pregnancy - one in the first trimester and one in the second. • The first trimester ultrasound is used by health care providers to confirm and date the pregnancy, so you will get a fairly accurate idea of your due date.
This ultrasound can also be used to check for the presence of more than one fetus. • The second trimester ultrasound scans for fetal malformations and, in some cases, is able to . It can also be used to check the position of the baby and the placenta, the baby's expected weight and the amount of amniotic fluid present. Schedule the appointment per your health care provider's instructions.
Your first ultrasound will usually be scheduled about 20 weeks into your pregnancy. Check with your health insurance provider to ensure the procedure will be covered and to determine where the exam must be performed. Some insurers require testing to be done at a medical lab, while others approve in-office ultrasounds. Drink 4 to 6 glasses of water before the exam.
A full bladder can change the position of the uterus by taking the flexion (bending movement) out of it and pushing it up so it is easier to scan. Also, the fluid in the bladder serves as a good medium for sound conduction. You will be asked to refrain from urinating until the exam is complete.
Relax and lie still during the exam. The technician will apply special gel to your abdomen and will glide a transducer on top of the gel. • The sound waves reflected off of your bones and other tissues will be converted into black-and-white or gray images on a monitor for measurement by the technician.
• You may be asked to hold your breath for just a few seconds several times during the exam, which should take about 30 minutes in total. • When complete, the technician will assist you with wiping away the conductive gel. Discuss the results of the ultrasound with your health care professional. Do not attempt to decipher the ultrasound images on your own, as they are nearly impossible to read by the untrained eye.
• According to the National Library of Medicine, normal results would show that the developing baby, placenta, amniotic fluid, and surrounding structures are normal in appearance and appropriate for the gestational age.
You may see this section attached with the ultrasound image written in a separate paper. Community Answer • You can't get an ultrasound done unless pregnancy has been confirmed, and even then, you usually need to wait until the 8th week of your pregnancy. Go to your local clinic or Planned Parenthood and take a pregnancy test there, if you want more immediate confirmation.
But your best bet is to call your doctor and ask about next steps. Community Answer • While it is not typical to have a negative pregnancy test and be missing your period, it does happen. However, there are other causes for this as well. It is recommended that you follow up with the doctor ASAP on your blood work results to ensure that you are not having a false negative home pregnancy test.
Blood tests for pregnancy are accurate, while home pregnancy tests may not be.
When to make the first ultrasound? Today sonographys (ultrasounds) are the most common, safe and highly effective method of assessing the development of embryos.
A fertilized egg can be seen in the womb 3 weeks after conception. This is due to trans-vaginal ultrasounds. Ultrasound in early pregnancy The length of the baby at 4 weeks old is no more than 5 mm.
Its heart rate reaches 100 beats per minute. By 6-7 weeks from the moment of conception the head and torso begin to develop. There are clearly defined arms and legs. Then the baby makes its first attempt to move independently. An important component of an ultrasound in early pregnancy is the study of the sac surrounding the baby. A relationship should formed between the baby and its environment. Without this, it is impossible to further the development of the pregnancy.
The first ultrasound during pregnancy should be carried out by a specialist. One who is very well-versed in matters of early prenatal diagnosis. Making sure that the baby is all right, he will be happy to help the parents see the eyes, ears and even the fingers and arms of their child. When to do the first ultrasound? Ultrasounds have been closely studied.
No harmful effects on babies come from ultrasounds. But the negative consequences of the refusal of the ultrasound in the first trimester are very evident. Every year in Moscow, about 100 children with Down syndrome are born.
Unfortunately, most people, including some doctors, do not know that using an ultrasound can show signs of issues in as little as 12-13 weeks. Why is it necessary to hold a session of the first ultrasound no later than this deadline? Firstly, it is optimal for diagnosing malformations and chromosomal pathology markers. Within 2 weeks the test can show suspected Down’s syndrome and other serious diseases that can later disappear. Secondly, in cases of suspected chromosomal abnormalities, doctors have time to hold a study and terminate the pregnancy if necessary.
Terms are an ultrasound Tests on all pregnant women have a specified time: 12-13 weeks, 22-23 weeks and 31-32 weeks. This allows you to quickly identify the widest range of possible fetal diseases and complications. As well as identifying further medical needs. The first genetic blood test is during the 12th to 13th week. Specialists can evaluate important points: the anatomical features of the fetus and the thickness of the neck area – a marker of Down syndrome.
The 22nd – 23rd week of pregnancy rules out defects in the brain, heart, kidneys, liver and the gastrointestinal tract. The 31st-32nd week is to diagnose malformations of organs like the heart. In addition, doctors determine the rate of fetal growth and what size to expect.
Can a baby's due date be a month off when determined by an ultrasound?