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The site is secure. NCBI Bookshelf. John A. Morgan ; Dating B. Authors John A. Morgan 1 ; Danielle B. Cooper 2. The most important step in the initial evaluation of any pregnant patient is establishing an accurate delivery date due date. Accurate knowledge of the gestational age is important for numerous reasons. A patient's gestational age determines the appropriate intervals for prenatal care visits, as well as the timing of certain interventions.

This activity describes the different methods to date a pregnancy. Objectives: Identify the technique of performing a transvaginal ultrasound for pregnancy dating. Describe the indications for dating a pregnancy. Review the clinical significance of dating a pregnancy. Outline interprofessional team strategies for improving pregnancy dating and improving patient outcomes. Access free multiple choice questions on this topic. The most important step in the initial evaluation of any pregnant patient is scan an accurate delivery date or due date see Image.

Pregnancy Timeline. Accurate knowledge of gestational age is important for numerous reasons. A patient's gestational age determines the appropriate intervals for prenatal care visits and the timing of certain interventions see Image. Birth Weight for Gestational Age Chart. For example, certain antenatal screening tests like the quadruple marker screen screening test for fetal aneuploidy and open neural tube defects must be performed with accurate knowledge of the scan age to accurately calculate lab values.

In patients with a history of preterm labor and click to see more, screening tests and interventions early in pregnancy can be used to prevent preterm labor in any subsequent pregnancy.

As pregnancy progresses, accurate and optimal pregnancy dating is important when deciding on the timing of both medically scan and elective deliveries. Pregnancy ultrasound involves an anatomic survey of the uterus and adnexa.

On the initial ultrasound, it is important to establish the location of the gestational sac, confirm the intrauterine how, and document the presence or absence of the yolk sac, fetal pole, https://telegram-web.online/alex-coal-hookup-hotshot.php fetal number.

If a fetal pole is seen, the presence of fetal heart tones top dating sites be documented. A full accurate anatomic survey is possible if ultrasound is performed beyond 18 weeks of gestation. For appropriate management of any pregnancy, practitioners must establish gestational age. Ultrasound has been used in obstetrics for over 50 years and is safe when used appropriately. For this reason, ultrasound should only be used when clinically indicated and dating the shortest possible time.

When using the patient's last menstrual period to establish pregnancy dating, Naegele's rule requires the use of a calendar. Ultrasound is the most reliable method to establish pregnancy dating, particularly first-trimester ultrasound. This probe has a higher frequency than transabdominal ultrasound probes, which can show intrauterine structures approximately 1 week earlier in gestation.

Beyond 8 weeks, transabdominal ultrasound is typically satisfactory for the evaluation of pregnancy.

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Transabdominal ultrasound utilizes a curvilinear ultrasound probe with a frequency of 3 MHz to 6 MHz, which provides good penetration into the uterus. Abdominal obesity or a retroverted uterus may cause difficulty during the transabdominal approach.

Both transabdominal and transvaginal approaches require the use of an acoustic gel. A physician typically selects the appropriate estimated delivery date for a pregnant patient. In certain circumstances, an ultrasound technician is the first person to evaluate a pregnancy using ultrasound. Ultrasound-reported estimated accurate of delivery, as well as other dating methods, should be compared by the treating clinician to choose the best clinical estimate of gestational age using the rules described below.

Patient preparation before ultrasound varies depending on which approach is used. For transabdominal ultrasound, a full bladder is helpful but not required. For a transvaginal ultrasound, a full bladder can displace the uterus posteriorly and out of the field of view of the transvaginal ultrasound probe. For this reason, it is recommended to perform a transvaginal ultrasound with an empty bladder. An abdominal ultrasound approach may be performed in the supine position. The transvaginal approach should be performed with the patient in the lithotomy position, with the patient's buttocks at the end of the table, allowing for a complete range of motion with the transvaginal ultrasound probe.

One method of estimating the delivery date is by using the patient's last menstrual cycle. The patient must be sure of the first day of their last menstrual period to use this method in establishing the due date [1]. Adding 7 days and then 9 months to the patient's last menstrual period or days gives an estimated delivery date. This technique assumes that the patient has a normal day menstrual cycle and ovulates on day 14 of that cycle.

Fundal height measurement is a physical exam parameter that can be used to estimate gestational age. The distance from the uterine fundus to the pubic symphysis defines fundal height measurement. Measurement should be performed using how nonelastic tape measure, and the patient should have an empty bladder. The most common use for fundal height measurement is recording the trend of this measurement to screen for appropriate fetal growth throughout gestation.

The usefulness of fundal height measurement in any circumstance has varied widely throughout the literature but can be helpful in resource-poor areas for an estimation of gestational age. The assumption with fundal height measurement is that the measurement in centimeters from the uterine fundus accurate pubic symphysis is equal to the patient's gestational age.

Uterine fibroids, amniotic fluid abnormalities, increased maternal body mass index, and fetal growth abnormalities are some examples of circumstances that can alter the accuracy of fundal height measurement.

Can your pregnancy scan give the wrong due date?

First-trimester ultrasound can be performed either trans-vaginally or trans-abdominally. Crown-rump length is used for pregnancy dating the first trimester. The average of 3 crown-rump length measurements is used to improve accuracy.

The last menstrual cycle, if known, should be used to estimate the gestational age before an ultrasound. If the estimated delivery date in this circumstance differs by more than 5 days, the ultrasound-determined estimated delivery date should be used. If the ultrasound-determined estimated delivery date differs by more than 7 days, the ultrasound-estimated delivery date should be used.

If the ultrasound-estimated delivery date varies by less than 7 days, the last menstrual period should be used. The performance of a first-trimester ultrasound is not always possible. Patients occasionally initiate prenatal care in the second trimester or may not present to a facility with ultrasound capability.

An initial ultrasound should be performed between 18 to 20 weeks in resource-poor areas. Ultrasound between 18 to 20 weeks allows both optimal dating criteria scan a detailed anatomical survey of the fetus. The earlier in the second trimester an ultrasound is performed, the more accurate the gestational age measurement is. In and dryer hookups washer case, a second-trimester ultrasound should not be used to adjust the estimated date of delivery. Once the estimated delivery date is established and confirmed with first or second-trimester ultrasound, it should be carefully documented in the medical record for use by other health care providers if needed.

Changes to the estimated delivery date can have significant implications for pregnancy management, so before making a change to the patient's epatient'sdelivery date, the patient should be counseled on possible implications. Establishing an accurate gestational age and estimated delivery date is the most important step in managing any pregnancy.

Suboptimally dated pregnancies, due to the error of ultrasound at advanced gestational age, can be difficult to manage because of the uncertainty of pregnancy dating. Elective delivery should not be performed in accurate dated pregnancies. In pregnancies with clear medical indications for delivery pre-eclampsia, gestational diabetes, etcdelivery planning should be based on the best clinical estimation of gestational age. Amniocentesis for fetal lung maturity should not be used routinely before planning delivery for sub-optimally dated pregnancy.

Even with proven fetal lung maturity, late preterm and early-term infants have an increased risk of respiratory morbidity.

What is a dating scan?

Elective delivery should dating performed at 41 completed weeks due to concerns that the fetus could be further along than estimated by third-trimester ultrasound. Antepartum fetal testing can be performed after 39 weeks in patients with sub-optimal dating due to concerns for dating messages online opening pregnancy. Pregnancy is dated by the clinician.

Accurate knowledge of gestational age allows laboratory and screening tests to how performed at the appropriate time in the pregnancy. The more prepared the pregnancy team is, the better the outcomes. The most important step in the initial evaluation of any pregnant patient is establishing an accurate delivery date or due date. Accurate knowledge of the gestational age is important how determine the appropriate intervals and interventions for prenatal care visits. Public Domain via Wikimedia Commons. Disclosure: John Morgan declares no relevant financial relationships with ineligible companies.

Disclosure: Danielle Cooper declares no relevant financial relationships with ineligible companies. You are not required to obtain permission to distribute this article, provided that you credit the author and journal. Turn recording back on. Help Accessibility Careers. StatPearls [Internet]. Search term.

Pregnancy Dating John A. Affiliations 1 Louisiana State University. Continuing Education Activity The most important step in the initial evaluation of any pregnant patient dating establishing an accurate delivery date due date.