How do dating ultrasounds work

This written information is for guidance only and does not replace consultation Ultrasound in early pregnancy (before 12 weeks) – Dating Scan. Ultrasound in early use ultrasound to work out how far along a pregnancy is and when the.
Table of contents

The results of ultrasound testing provide you and your health care provider with critical information about you and your baby.

How is an ultrasound performed?

The Society of Obstetricians and Gynaecologists of Canada recommends that all women have two ultrasounds: See below for descriptions of the information gathered from these two types of ultrasounds. Ultrasound uses high-frequency sound waves to create images of the inside of the body.. The technique does not use any radiation.

Ultrasound: Sonogram

It is safe, painless and relatively quick test that usually takes around 30 minutes. The technician will put a warm gel on your abdomen and use a scanning device to get the ultrasound images. Sometimes the ultrasound must be done through the vagina; this procedure may be uncomfortable, but is not considered painful.

You will be asked to lie on your back while a technician rubs a warm gel on your belly. The gel allows the transducer a handheld device that looks like a microphone to slide more easily over your belly and improves the transmission of sound waves into your body. The sound waves bounce off various surfaces within your body -- including your baby -- as vibrations.

First Trimester / Dating Ultrasound

The echoes are translated into electrical signals that are projected as pictures onto a monitor for viewing. An abdominal ultrasound poses no risk to you or your baby. In fact, there are many benefits to checking on your baby's development during pregnancy. If you need an ultrasound early in pregnancy, it may be necessary to use a vaginal probe a transducer placed in the vagina. This allows the technologist to view your uterus through the cervix.

What types of ultrasound are there?

This method may also be used later in pregnancy to locate your placenta if it's over the cervix or to measure the length of the cervix. Vaginal probes may cause a sensation of pressure but shouldn't adversely affect your pregnancy. 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.


  • my ex is dating someone else to make me jealous!
  • Routine ultrasound.
  • Methods for Estimating the Due Date.
  • dating oral herpes!

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.


  • dating a guy 3 years younger than you!
  • two first borns dating!
  • Methods for Estimating the Due Date - ACOG;
  • how to ask for her number online dating!
  • mobile simple hookup!
  • girlfriend has profile on dating site!

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.

First Trimester / Dating Ultrasound | Advanced Women's Imaging

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.

How to use ultrasound in pregnancy

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.

Why would I have a dating scan?

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.