A thin line of hair along the fetal back (arrows) is seen. Note the differences in their appearance depending on the level. Then, your obstetrician will do their own analysis before meeting with you and sharing results. FIGURE 1.36: A: Sagittal section of a fetal head at 22 weeks gestation with a cavum veli interpositi (notched arrow) located posteriorly and inferiorly to CSPV (asterisk). FIGURE 1.47: Sagittal view of the spine in mid-second trimester demonstrating its normal curvature. Additional fetal biometry is performed if clinically appropriate. FIGURE 1.12: Transverse view of the chest at 12 to 13 weeks gestation containing a four-chamber heart view. 1.37).96 In the sagittal view, visualization of the pericallosal artery helps to confirm the presence of the corpus callosum (Fig. A 20-week ultrasound, sometimes called an anatomy scan or anomaly scan, is a prenatal ultrasound performed between 18 and 22 weeks of pregnancy. It should be remembered that the anterior pillars of the fornices lie in the same general area as the CSP. All fetal anomaly codes begin with a maternal code followed by a fetal code. In addition to measuring the BPD and HC, the occipitofrontal diameter (OFD) can be measured and expressed in ratio to the BPD (BPD/OFD) as the cephalic index (CI) (Fig. The four-chamber view can be reliably obtained in 95% to 98% of pregnancies and theoretically detects >50% of serious cardiac malformations when performed in mid-gestation. 1.46). in an anatomical survey of 298 fetuses at 12 + 0 to 13 + 6 weeks of gestation 13. FIGURE 1.33: Posterior coronal view of the brain at 24 weeks gestation. If you are seeing your healthcare provider afterward, your appointment could last up to 75 minutes. Absence of normal operculization raises the possibility of a neuronal migration defect such as lissencephaly. Since the cerebellar vermis is not yet fused, a large midline communication is seen between the developing fourth ventricle and the cisterna magna (CM) (Fig. At 20 weeks of gestation, it is recommended that pregnant women have an ultrasound to confirm if the fetus is alive, measure growth, detect uterine or placental abnormalities, assess fluid volume, and image all fetal organ systems to detect any abnormalities. This is the fetus's penis and testicles. Policy. Measurement according to standardized methodology allows individualized levels of risk for trisomy 21, 18, and 13 to be calculated. The fetal head and upper torso occupy the majority of the image, and the fetus is in a neutral position. While the 20-week scan can detect certain conditions, it cant identify everything. A finding that is commonly seen in the early first trimester and that deserves special mention is physiologic herniation of the midgut into the root of the abdominal cord insertion (Fig. This is a normal variant and is part of the leptomeningeal space between the roof of the third ventricle and the body of the fornices. This . Salomon LJ, Alfirevic Z, Berghella V, Bilardo C, Hernandez-Andrade E, Johnsen SL. The paired laminar ossification centers are slightly offset from the midline. This represents the choroid plexus. The sagittal section offers the best view of the fetal forehead. As a normal variant, the CSV can be unusually large and visible in this section. The technician will confirm that your baby's spine and neural tube are completely formed and without cysts. Ultrasound code selection is based on the gestational age, number of fetuses, and medical necessity. Employing the transvaginal route to image a fetus that is cephalic in presentation can facilitate a detailed examination of the intracranial anatomy. Most of the time, a prediction is made only when the technician is certain of sex. This is normally done at the level of the posterior margin of the choroid plexus using a magnified image so that calipers can be accurately placed on the inner margins of the ventricular walls (Fig. Conduct a systematic ultrasound fetal anatomy scan and measure/document all pertinent anatomic structures. - know how to measure bip. Placental site and cervical length can then be assessed, although true cervical assessment requires a transvaginal approach, which is best performed at the end of the examination. Components congenital diaphragmatic herniation: fetal stomach may be absent in an axial ultrasound scan - standard view due to migration into the thorax. FIGURE 1.5: Sagittal view of a 12- to 13-week fetus. Using a single ultrasound examination in the second trimester to assist in determining the gestational age enables simultaneous fetal anatomic evaluation. The genital tubercle (open arrow) points in a direction parallel to the longitudinal axis of the fetus, indicating a female gender. Some healthcare providers recommend eating or having a full bladder to make it easier to see the images and make the fetus more likely to move. Bethune M, Alibrahim E, Davies B, Yong E. A pictorial guide for the second trimester ultrasound. This will be one of your longer appointments around 45 minutes for just the ultrasound. FIGURE 1.2: Embryo at 6.5 weeks gestation. A 20-week prenatal ultrasound is considered medically necessary to detect potentially life-altering anomalies. This is because of the fact that they are the easiest to obtain and are very familiar to operators who are involved in fetal scanning. FIGURE 1.40: A: Axial section of a fetal head at 20 weeks gestation demonstrating the insula at an early stage of operculization (open arrow) with the middle cerebral artery (color Doppler) at its base (solid arrow). The transvaginal approach should be used in all circumstances where a viable intrauterine pregnancy is not obvious on transabdominal assessment. In the anteroposterior axis, the spine is curved, being convex in the thoracic region and concave in the lumbosacral region. Since the CSPV is arched in shape, may appear to be separate from the cavum septi pellucid, simulating a cyst (Fig. The general symmetry of the fetal brain is first assessed using standard axial views. FIGURE 1.4: Sagittal view of an 11- to 12-week fetus. Color Doppler may be used to help define the cord insertion and the number of arteries in the cord (Fig. B: Sagittal section of a fetal head in the early third trimester. The bladder should be visible in all cases from 12 weeks onward. Anatomy scans are usually a positive experience. The posterior fossa anomalies are one area where a fetal MRI may be especially helpful in arriving at the correct diagnosis. If there is non-visualization of the fetal stomach >18 weeks, there is an 85% chance of an abnormality. 1.29). Ask your ultrasound technician if you are unsure what you are looking at. The calvarium will be completely absent in anencephaly. Talk to your healthcare provider about any concerns you have so they can offer reassurance and ease your worries. The physician or other qualified healthcare professional may perform an ultrasound on a patient in her first trimester to determine the number of sacs and to survey the fetal structures, amniotic fluid, and maternal structure. The importance of positively identifying the CSPV lies in the fact that it can be absent in association with midline defects. 1.44). In case of any suspected genetic abnormality, it may be necessary to perform an ultrasound during the second or third trimester of pregnancy. The abdominal circumference (AC) is a transverse section (coronal) through the fetal abdomen at the level where the umbilical vein enters the liver. EIF appear to be caused by deposits of calcium in the muscles or tendons of the heart. The AC may be measured directly, or calculated from the AP and transverse abdominal measurements. The vertebral body ossification center is round and is located in the midline. The kidneys are generally difficult to see owing to their small size and echogenicity, which is similar to that of the small bowel. The shape of the skull may be abnormal in association with a number of specific fetal anomalies. In longitudinal section, the line of ossification of vertebral bodies is seen anteriorly and, if there is a slight oblique cut, one set of posterior ossification sites will be visualized. 1.11). It is normally small (<3 mm diameter) and may be difficult to visualize. B. Often, the region of interest can be effectively identified using grayscale prior to employing Doppler, resulting in reduced energy exposure to the fetus. 1.39). Please note the increased echogenicity of the roof of the third ventricle extending into the foramina of Monro. In the early first trimester, the transvaginal approach is ideal to detect any adnexal pathology or free fluid. Each lateral ventricle is divided into five parts: The frontal horn, the body of the lateral ventricle, the occipital horn, the inferior (temporal) horn, and the atrium (trigone). Absence of an ossified calvarium in association with abnormal intracranial anatomy is consistent with exencephaly/anencephaly sequence. FIGURE 1.41: Axial view of a fetal head in the third trimester after the completion of insular operculization. The OB/GYN Ultrasound - Core Series is comprised of lectures given by a renowned physician and sonographer. Where applicable, a 7th character is to be assigned to the In this section, the intracranial anatomy essentially consists of the lateral ventricles and a very thin layer of brain parenchyma. C: Section demonstrating vertebral arch ossification centers (solid arrows) only. The accuracy of CRL measurement decreases with gestational age. FIGURE 1.32: Midcoronal view of the brain at 24 weeks gestation. As the transducer is moved caudally, the orbits can be identified. Fetal echocardiography in experienced hands has been reported to detect up to 90% of serious CHD in low-risk populations. ASSESSING FETAL ANATOMY DURING THE SECOND AND THIRD TRIMESTERS. In the coronal view, the two lateral points of ossification can be visualized cleanly, and by moving the probe anteriorly, ossification of the vertebral body can be brought into view. Gharekhanloo F. The ultrasound identification of fetal gender at the gestational age of 1112 weeks. The sacral portion of the spine usually has a more persistent curvature, with the tip of the spine pointing posteriorly (Fig. Other than finding out the sex of your baby (if you want to know), the ultrasound technician. Among all these exams, you will find the Fetal Anatomy scan an ultrasound that has to be done between 18 and 22 weeks of pregnancy. A: Arrow, developing aqueduct of Sylvius; bs, brain stem. The scan also looks for signs of specific congenital disabilities or structural issues with certain organs. ultrasound units for a fetal anatomic survey in the second trimester Received 13 April 2006; revised 15 September 2006; accepted 29 September 2006; published online 2 November 2006 FIGURE 1.28: Right parasagittal section of a fetus at 12 to 13 weeks gestation with color and pulsed Doppler. Both individual vertebrae and their skin covering should be evaluated by sliding the transducer along the entire length of the spine. Similar results were reported by Braithwaite et al. The issue of fetal biometry is discussed in this chapter only to illustrate the proper technique rather than clinical applicability. anatomical survey using transvaginal scanning at approx-imately 13-16 weeks' gestation. The maternal cervix and adnexa should be examined. Not infrequently, the cavum septi pellucidi et vergae (CSPV) contains septations, especially in its posterior portion (Fig. B: Slightly more caudal section of the same fetus demonstrating the course of the middle cerebral artery (solid arrow) to the base of the insula (open arrow) with color Doppler. Fetal ultrasonography is an essential element in the evaluation of anomalies and fetal well-being throughout pregnancy. This involves evaluation of the vertebrae and the contents of the spinal canal. 1.17). Every attempt should be made to visualize both cerebellar hemispheres to allow a comparison of their size and echotexture. B: Axial view in a plane slightly caudal to A, where the cavum septi pellucidi (solid arrow) and cavum septi vergae (open arrow) are seen as two separate structures. The second trimester ultrasound is commonly performed between 18 and 22 weeks gestation. These diagnoses can be difficult to tease out and depend on findings in axial, midsagittal, and coronal sections. FIGURE 1.27: Transverse/oblique section of the lower abdomen and the pelvis showing the urinary bladder (b) with two umbilical arteries coursing around it in a 12- to 13-week fetus. FIGURE 1.7: Transverse views of a fetal head at 12 weeks gestation demonstrating hindbrain appearance at various levels in descending order. The American College of Obstetricians and Gynecologists. 1.47). In an axial section at the superior aspect of the thorax, clavicles can be seen even early in gestation (Fig. Crossref, Medline, Google Scholar; 10 Braithwaite JM, Armstrong MA, Economides DL. 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