High-frequency sound waves travel from the probe through the gel into the body. The probe collects the sounds that bounce back. A computer uses those sound waves to create an image. Ultrasound exams do not use radiation x-rays. Because ultrasound captures images in real-time, it can show the structure and movement of the body's internal organs.
The images can also show blood flowing through blood vessels. Obstetrical ultrasound provides pictures of an embryo or fetus within a woman's uterus, as well as the mother's uterus and ovaries. Doppler ultrasound is a special ultrasound technique that evaluates movement of materials in the body.
It allows the doctor to see and evaluate blood flow through arteries and veins in the body. During an obstetrical ultrasound the examiner may evaluate blood flow in the umbilical cord or may, in some cases, assess blood flow in the fetus or placenta.
Some physicians also use 3-D ultrasound to image the fetus and determine if it is developing normally. You should wear a loose-fitting, two-piece outfit for the examination. Only the lower abdominal area needs to be exposed during this procedure.
The radiologist or sonographer may elect to examine an early pregnancy by means of transvaginal ultrasound in order to see the pregnancy more closely or to assess the cervix. For more information on transvaginal ultrasound, see the Pelvic Ultrasound page.
Ultrasound machines consist of a computer console, video monitor and an attached transducer. The transducer is a small hand-held device that resembles a microphone. Some exams may use different transducers with different capabilities during a single exam.
The transducer sends out inaudible, high-frequency sound waves into the body and listens for the returning echoes. The same principles apply to sonar used by boats and submarines. The technologist applies a small amount of gel to the area under examination and places the transducer there. The gel allows sound waves to travel back and forth between the transducer and the area under examination. The ultrasound image is immediately visible on a video monitor.
The computer creates the image based on the loudness amplitude , pitch frequency , and time it takes for the ultrasound signal to return to the transducer. Ultrasound imaging uses the same principles as the sonar that bats, ships, and fishermen use. When a sound wave strikes an object, it bounces back or echoes.
By measuring these echo waves, it is possible to determine how far away the object is as well as its size, shape, and consistency. This includes whether the object is solid or filled with fluid. Doctors use ultrasound to detect changes in the appearance of organs, tissues, and vessels and to detect abnormal masses, such as tumors. In an ultrasound exam, a transducer both sends the sound waves and records the echoing returning waves. When the transducer is pressed against the skin, it sends small pulses of inaudible, high-frequency sound waves into the body.
As the sound waves bounce off internal organs, fluids and tissues, the sensitive receiver in the transducer records tiny changes in the sound's pitch and direction. Your doctor will discuss this with you, and we encourage you to ask any questions you might have. For your convenience, we offer on-site obstetric ultrasound at all of our office locations — so your ultrasound exam s can be scheduled on the same day as your doctor visits in most cases.
Additionally, we want you to know that our sonographers and physicians are certified by the American Institute of Ultrasound in Medicine — so you can feel confident that your test is being administered and interpreted by specially trained experts who have met rigorous standards for quality and competency. We are happy to answer any questions you have about ultrasound exams during pregnancy.
Simply contact us. View Location Details. Obstetric Ultrasound. Reasons for an Obstetric Ultrasound. Types of Obstetric Ultrasound Scans:. What Happens During my Obstetric Ultrasound?
The sonographer will apply a warm, hypoallergenic ultrasound gel to your abdomen and move a transducer around your belly to gather images of the fetus. The sonographer will move the transducer around the target area with moderate pressure to obtain images. This pressure should not cause pain.
Please inform your sonographer of any discomfort. If you are having trouble holding your bladder or are in an uncomfortable position, talk to your sonographer so we can make adjustments.
During your scan, the sonographer will be concentrating on completing your medical exam in a timely and coherent manner; therefore, try to save your questions for the end of the exam. At the end of your exam, we will print some ultrasound images, and we can also send digital photos to your cell phone or email for maximum convenience. A radiologist will review the images and send a detailed report to your doctor, usually within one business day.
Important Notes. Sometimes you will be scheduled for additional scans. These follow-up scans do not mean there is a complication with your baby! Sometimes the gestational age or position of the fetus inside the uterus makes it challenging to take the right photos for diagnosis. Usually, in these situations, we will schedule a follow-up appointment.
Pictures or videos are not allowed inside the exam room. Please respect the privacy of our staff and the sensitive nature of the health care industry. Support from Significant Others. Legally, health care technologists are not permitted to discuss results with the patient.
Resulting images are reviewed by our radiologists, who have over 13 years of post secondary education plus additional years of specialization and industry experience. Our radiologists forward their reports to your doctor, who will often combine their information with results from additional tests and your patient history to form a comprehensive diagnosis.
Your doctor will review everything with you in private and determine the next steps in your health care journey. Ultrasound Baby Pictures.
At Insight Medical Imaging, we can provide photos in three ways: Physical copies printed at our clinics Digital copies texted to your mobile device Digital copies sent to your email We encourage patients to take both digital and physical copies of their ultrasound photos. Twins or Multiples. Detection of Multiples. What About a Second Heartbeat? For example: Your own heartbeat can complicate the detection process. Varying development timelines mean some heartbeats are hard to detect until the end of the first trimester.
Impact of Multiples on Scan Time. Obstetric Ultrasound Side Effects and Risks. Obstetric Ultrasound Scans:. Dating Ultrasound. Purpose of a Dating Ultrasound. Is a Dating Ultrasound Internal or External?
Typically, your doctor will use your LMP if it has been reliably identified. Sometimes your doctor will use your dating ultrasound to determine your due date. Your doctor might also rely on your dating scan if your cycle is irregular or if you have recently been on a birth control pill. Both factors can affect ovulation and conception timelines, making your LMP less reliable. Nuchal Translucency NT Measurement. The NT ultrasound also: Confirms that the baby has a consistent heartbeat Confirms your dates Diagnoses a multiple pregnancy Checks for other congenital disabilities.
The Maternal Blood Test. Benefits of FTS. Early, more accurate screening gives peace of mind to many women. The FTS personal risk estimate can be used to help women make more informed choices about diagnostic testing. It is possible to detect specific, significant congenital disabilities at the time of the NT scan.
Limitations of FTS. Often, the bone casts a shadow to help identify this landmark Fig. Because the reference tables were derived in this same fashion, accuracy is preserved. The femur shown here is measured from blunt end to blunt end parallel to the shaft.
The epiphyses are not seen and not measured normally. The acoustic shadowing may be seen projecting downward from the bone. As is the case with BPD, the reliability of femur length in prediction of gestational age is best in early pregnancy.
In the third trimester, however, femur length shows less variation than the BPD. Femur length may be difficult to obtain in a breech presentation, and measurement of the fetal humerus provides a good alternative.
The humerus usually can be identified arising from the lateral upper fetal chest. The fetal abdominal circumference, or mean abdominal diameter, also is useful in predicting gestational age.
The fetal image in this traverse plane is nearly circular; the abdominal circumference is the average of the anteroposterior and transverse diameters, measured from the outer diameter to outer diameter. This image is from a scan plane perpendicular to the fetal trunk at the level of the umbilical vein uv and stomach st. This is appropriate for the measurement of the abdominal circumference as shown.
The transverse spine sp also is visible. The relation between ultrasonographically derived fetal dimensions and gestational age is purely empiric. The older a normal fetus is, the larger its dimensions are.
The reproducible ultrasonographic measurement of any fetal dimension in a normal reference population of fetuses of known gestational age allows the construction of a regression relation between that dimension and age. Subsequently, the determination of the gestational age of a pregnancy for which the conception date is unknown can be made by comparing that dimension with the reference data Table 1.
Gestational age wk Biparietal diameter mm Femur length mm Humerus length mm Head circumference mm Average head d iameter mm Abdominal circumference mm Average abdominal diameter mm 14 28 15 15 0 32 0 84 0 27 15 32 18 18 0 36 0 93 0 30 16 36 20 21 0 41 0 34 17 39 23 23 0 45 0 37 18 42 26 26 0 49 0 41 19 45 29 28 0 53 0 44 20 48 32 31 0 57 0 48 21 51 35 33 0 61 0 51 22 54 37 35 0 65 0 55 23 58 40 37 0 68 0 58 24 61 42 39 0 72 0 62 25 64 45 41 0 76 0 65 26 67 48 44 0 79 0 69 27 70 50 46 0 82 0 72 28 72 53 48 0 86 0 76 29 75 55 49 0 89 0 79 30 78 57 51 0 92 0 83 31 80 60 53 0 95 0 86 32 82 62 55 0 97 0 90 33 85 64 57 0 93 34 87 67 59 0 97 35 88 69 60 36 90 71 62 37 92 73 64 38 93 76 66 39 94 78 67 40 95 80 69 Rockville, MD, Aspen, Averaging the gestational ages derived from two or more measurements has been shown to be more accurate than using any single parameter.
Because of the greater accuracy of the early study, ultrasound examinations subsequent to an early study should not be used to revise the estimated date of confinement EDC , but rather should be used as a measure of the quality of fetal growth between the two studies. Similarly, it is not appropriate to revise an EDC on the basis of an ultrasound examination if the patient's menstrual dates are within the range of error of the ultrasound method.
If significant discrepancy is seen between two ultrasonographically measured fetal dimensions more than a 2-week difference , then the ultrasonographer must consider the possibility of an error in measurement technique.
If a critical reevaluation reveals no error, then asymmetry in fetal growth may be present. Growth asymmetry may occur as a result of physiologic alteration in fetal head shape brachycephaly or dolichocephaly or in association with intrauterine growth restriction IUGR , macrosomia, or a fetal anomaly. A basic ultrasound examination should contain a fetal survey, an evaluation of fetal biometry, and an anatomic screening examination. The survey includes a confirmation of fetal number, viability, position, assessment of amniotic fluid volume, and location of the placenta.
In assessing fetal biometry, the applicable standard fetal measurements already discussed, including CRL, BPD, abdominal circumference, and femur length, should be taken. The estimation of fetal weight is a clinically useful parameter computed from the fetal biometric measurements.
Several equations have been produced based on fetal biometry that estimate fetal weight. One or more of these usually is incorporated into the software of most contemporary ultrasound machines. An estimation is provided automatically after the biometry is recorded. An ultrasound examination also should include specific documentation of the fetal anatomic images obtained.
These images are usually stored in the form of Polaroid pictures, videotape, thermal prints, or digital image files.
Generally recognized indications for obstetric ultrasound imaging are found in Table 2. Although the routine use of ultrasound in early pregnancy is not considered the standard of care by any public organization in the United States, 9 it is promoted by many practitioners. Some investigators have noted a significant reduction in the frequency of labor induction for postdate fetuses when routine ultrasound is performed. Routine ultrasound use may decrease the incidence of antepartum fetal assessment and induction of labor for postdate fetuses.
Belfrage and colleagues 10 compared the routine use of ultrasound in early pregnancy with the use of ultrasound for selected indications. There also was a significant reduction in the incidence of labor induction for postdate fetuses in the routine ultrasound group.
Neonatal outcome was similar in both groups. The use of ultrasound as a routine screening tool in obstetric patients applies to low-risk patients who have none of the indications shown in Table 2. The study concluded that there was no benefit from routine ultrasound in this low-risk population.
The RADIUS study has been criticized in that the patients selected for final inclusion in this study bear little similarity to the average obstetric population. Only approximately one third of fetal anomalies were detected antenatally. Clearly, the detection of anomalies in tertiary centers was significantly more accurate than those in primary care ultrasound clinics. The Helsinki ultrasound trial included women: half were randomly allocated to ultrasound screening and half to routine obstetric care.
It also appeared in this trial that twin pregnancies detected earlier had a lower perinatal mortality rate. Clearly, the use of ultrasound as a screening test is a controversial matter.
The most likely benefits of ultrasound screening in low-risk patients are obstetric and include confirmation of dates, early detection of multiple gestation, location of the placenta, and baseline growth data. In virtually every complication that may occur later in pregnancy, clinical decisions may be facilitated if the patient had an ultrasound earlier in pregnancy. To be used as a screening test, ultrasound should be widely available and have a relatively low cost and high sensitivity and specificity rates.
One of the stated intents of the RADIUS study was to determine whether routine ultrasound screening would improve perinatal outcome. Ultrasound, however, is a diagnostic modality, not a therapeutic one.
Ultrasound alone cannot reduce perinatal mortality, but the information obtained from an ultrasound can be used to guide the clinician to choose the appropriate therapy. In the final analysis, whether ultrasound is used as a screening test may depend on its cost.
Direct cost savings from screening ultrasound examinations may be closely related to the accuracy of these examinations in detecting fetal anomalies.
One study concluded that cost-savings from screening ultrasounds in low-risk patients could only be realized if examinations were performed in tertiary centers. In the RADIUS study, approximately two-thirds of the subjects were thought to have an obstetric indication for ultrasound; however, it is only in the small proportion of truly low-risk patients that a screening ultrasound should be considered.
Should every obstetric patient have a routine ultrasound examination? Only if it is adequately performed, properly recorded, and the patient is counseled regarding appropriate goals and limitations of ultrasound. Routine screening is best performed between 18 and 20 weeks' gestation.
At this time, the fetus usually is large enough that the fetal anatomy can be surveyed well, and yet the gestation is early enough that the accuracy of biometric measurements is preserved. The introduction of maternal serum alpha feto-protein AFP screening gave rise to a two-tiered system of ultrasound. The basic, screening, or level 1 ultrasound was performed to assess fetal biometry and rule out multiple gestation.
A level 2, referral, high-detail, or targeted scan, performed by a more experienced sonologist, could then assess for fetal anomalies. The distinction between a level 1 scan and level 2 scan has blurred in modern practice, and there is no official credentialing for referral ultrasound. We believe that all ultrasound examinations should have at least a minimum content to include: documentation of fetal number, position, placentation, fluid volume, assessment of biometry, and cardiac activity.
The report should also include what anatomic features were noted and whether they appeared normal; images should be recorded. Although anomalies may be missed at all imaging centers, it is clear from the RADIUS study that tertiary centers have increased accuracy in detection, which may allow for optimizing perinatal care.
First-trimester ultrasonography can be of significant value in predicting the outcome in patients with bleeding in early pregnancy. Except in the unusual circumstance of a combined pregnancy incidence 1 in 12, to 30, , the finding of a pregnancy within the uterus excludes an ectopic pregnancy.
This distinction, however, is not always clear. The normal gestational sac has a well-defined, echogenic border. In ectopic gestation, decidua and blood may distend the uterine cavity, and the ultrasound image can mimic a gestational sac, resulting in the so-called pseudogestational sac. These entities often can be distinguished by ultrasound; in a pseudogestational sac, the echogenic rim usually is absent, ill defined, or not centrally positioned in the uterus.
In questionable cases, serial growth of the sac can be assessed. In a normal pregnancy, the gestational sac should grow at least 0. Using a quantitative assay of human chorionic gonadotropin hCG with ultrasound improves diagnostic accuracy. In practice, a clinical problem often faced is differentiation of a threatened abortion from an ectopic pregnancy. Ultrasound findings in a pregnancy destined to abort include a poorly-defined gestational sac, a large yolk sac 6 mm or greater in size , a low site of sac location in the uterus, or an empty gestational sac at 8 weeks' gestational age the blighted ovum.
The only absolute assurance that a pregnancy is intrauterine is the finding of a fetal pole within the uterine cavity. The endovaginal ultrasound can be useful in this clinical setting because the fetal pole can be seen at 6 weeks. In a normal pregnancy, the fetal pole should be visible if the gestational sac is 25 mm or larger in diameter.
The presence of a fetal pole with demonstrable cardiac activity is reassuring and greatly decreases the likelihood of spontaneous abortion. Endovaginal scanning provides superior resolution of the nonpregnant or very early pregnant pelvic organs. This is a midline endovaginal view of an anteflexed uterus filled with clusters of tiny anechoic areas and is the image of a hydatidiform mole Mo.
The outline of the mole is indicated arrowheads. The transducer in the vaginal fornix is at the top of the image, the maternal abdominal wall is to the left, and the cul-de-sac would be to the right. In , the American College of Ob Gyn endorsed offering aneuploidy screening to all gravidas. In fetuses with increased nuchal translucency and normal chromosomes, there is an increased incidence of fetal cardiac anomalies. Fig 7. Measurement of first trimester fetal nuchal translucency.
Absence of the fetal nasal bone in the first trimester at 11 or more weeks' gestation has been observed to occur more frequently in fetuses with Down syndrome. Although this is not as an important sonographic marker as increased nuchal translucency, fetuses with Down syndrome are more likely to have an absent nasal bone then chromosomally normal fetuses. These biochemical markers are used as a screening test for fetal anatomic abnormalities and Down syndrome.
0コメント