Fetal Measurements, Biometry Anatomy PDF

SECOND & THIRD TRIMESTERS Fetal Biometry and Growth General Guidelines View cardiac activity at beginning of each study to ensure that fetus is alive If fetal demise or obvious anomaly initially recognized, sonographer is better prepared to perform study and involve physician immediate...

SECOND & THIRD TRIMESTERS Fetal Biometry and Growth General Guidelines View cardiac activity at beginning of each study to ensure that fetus is alive If fetal demise or obvious anomaly initially recognized, sonographer is better prepared to perform study and involve physician immediately 2 Second and Third Trimester Protocol  !!!Check Fetal Cardiac Motion/Fetal Heart Rate Cervix – length should be greater than 3 cm Presentation and Lie  Measurements: BPD/HC, AC, FL, HL, Cereb./CM, Lateral Ventricles, AFI  Embrace your ADD 3 Basic Protocol Cardiac activity Number of fetuses Estimation of Fetal Age Biometry Measurements to include: BPD, HC, AC, FL,HL Fetal position  Basic Protocol Placental Cord insertion Number of vessels in cord Kidneys AB cord insertion Bladder Stomach 4-chamber heart/outflow tracts Placental position  2nd & 3rd Trimester Ultrasound Cerebral ventricles – measure width Cerebellum - measure Cisterna magna - measure Spine Diaphragm and heart situs 12 long bones, hands, feet  Cervical Length  Measure the length of the cervix from the internal to the external os  Do not use a transabdominal measurement if you cannot see the cervix clearly  You can do a transvaginal or a translabial approach to visualize the cervix  Cervix should be 3 cm or longer  Cervical Length If funneling is present, you should measure the length of the FUNCTIONAL cervix. Fetal Presentation Described in relation to maternal long axis When fetal lie is oblique, generally described by stating which quadrant of uterus contains fetal head and direction and position of fetal spine 11 Fetal Presentation Vertex/cephalic Head down Also relationship of fetal occiput to maternal pelvis Breech Frank breech may be turned Complete breech needs c-section May be described in relation of fetal sacrum to maternal pelvis Transverse If this lie in late pregnancy, look for mass or placenta previa- some reason preventing movement into vertex/cephalic presentation 12 Type of Breech Footling 13 Complete Breech Complete breech. Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by Mosby, an 14 imprint of Elsevier Inc. Incomplete Breech/Footling 15 Frank Breech Frank breech. 16  Situs Situs Solitus –a term for normal situs Right and left sides of fetus need to be conceptualized to ensure normal situs (positioning) of fetal organs Gallbladder on right side and apex of heart pointing toward fetal left side Fetal aorta lies slightly to left of midline, anterior to spine, and IVC is to right of midline and slightly more anterior to aorta 17 DA- descending aorta 18 Situs- TRV Dual Screen cannot alter probe Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by Mosby, an 19 imprint of Elsevier Inc. Situs-Long 20 Also use the aorta Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by Mosby, an 21 imprint of Elsevier Inc. Fetal Anatomy – Cranium ossifies by 12th week Check contour of skull bones circle at highest levels; oval shape as you move down pathology or fetal death may distort normal shape of skull Brain structures are more hypoechoic due to high water content Sulcus and gyrus- more echogenic Becomes more complex as the pregnancy progresses 22 Cranial Anatomy Cerebellum Choroid plexus Cisterna magna Lateral ventricles Midline falx CSP (cavum septum pellucidum) 23 The Cranium Midline falx is important landmark to visualize because its presence implies that separation of cerebrum has occurred 24  The Cranium There are three major scan planes for the fetal brain which accommodate 3 views: All are axial (transverse) of the fetal head with the exception of the cerebellar view, which is axial/oblique.  1. Thalamic view  The thalamic view is taken at the level of the biparietal diameter (BPD) and head circumference (HC) measurements  2. Ventricular view  The ventricular view is obtained through the atrium of the lateral ventricle.  3. Cerebellar view  The cerebellar view is angled through the posterior fossa (cisterna magna). 25 Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by Mosby, an 26 imprint of Elsevier Inc.  Other planes include the sagittal, parasagittal, and coronal which may be useful or necessary to define anatomy as required.  Ventricular View: Fetal ventricular system consists of two paired lateral ventricles, midline third ventricle, fourth ventricle adjacent to cerebellum contain cerebrospinal fluid (CSF) Choroid plexus tissue within lateral ventricles produces CSF  located within roof of each ventricle except at frontal ventricular horns 28  The Cranium: Lat Vents Measure posterior horn of lat. Ventricle (atrium) When measuring ventricle, measure directly across posterior portion, measuring perpendicular to long axis of ventricle rather than the falx, while placing calipers at junction of ventricular wall and lumen or cavity of ventricle Normal atrium measures 6.5 mm If atrium measures >10 mm, warrants serial imaging and further evaluation will be needed 29 The Cranium: Choroid Plexus 31 Thalamic View: Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by Mosby, an 33 imprint of Elsevier Inc. 36 Nuchal Skin Fold In second trimester, thickness of nuchal skin fold measured in plane containing cavum septi pellucidi, cerebellum, and cisterna magna Values of skin thickness of 5 mm or less up to 20 weeks’ gestational age normal Fetuses with thickened nuchal skin at increased risk for aneuploidy Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by Mosby, an 37 imprint of Elsevier Inc. The Thorax Evalute: Fetal breathing Size, texture, and location matter Solid, homogeneous masses of tissue Bordered medially by heart Laterally by rib cage Inferiorly by diaphragm 39 The Thorax Homogenenous lungs lateral to the heart (H) and superior to the diaphragm (arrows). S, Stomach; L, lungs; P, placenta. Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 40 Mosby, an  The Heart Lies more transversely in fetus than in adult because lungs are not inflated Apex of heart directed toward left anterior chest, with right ventricle closest to anterior chest wall and left atrium closest to spine Four chambers may be seen in view taken with beam perpendicular to septum or in view with beam perpendicular to valves Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 41 Mosby, an The Heart Four- chamber view: locate fetal stomach in transvers e, then angle towards Copyright © 2012, the head. 2006, 2001, 1995, 1989, 1983, 1978 by 42 Mosby, an The Heart In four-chamber view of heart, important to assess following: Cardiac position, situs, axis Apex of heart should point to fetal left side Presence of equal sized right and left ventricle Equal sized atria Interventricular septum Normal placement of tricuspid (right) and mitral valves (left) Normal rhythm and rate 43 The Heart – finding of an echogenic foci Echogenic structure, as bright as bone, that appears within cardiac chamber and persists despite changes in transducer position called echogenic intracardiac focus (EIF) Normal variation appears in many normal pregnancies May be, however, associated with increased Copyright © 2012, risk of aneuploidy and cardiac defects 2006, 2001, 1995, 1989, 1983, 1978 by 44 Mosby, an Echogenic focus Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 45 Mosby, an Fetal Cardiology AIUM / ACR standards in the 2nd and 3rd trimesters include:  Four chamber view  Position of fetal heart in the thorax LVOT and RVOT not yet part of standards 4 chamber view alone: 33-63% sensitive to detection of anomalies With outflow tracts: 83-85% sensitive Four Chamber View – label/ID each chamber! 47  The Four Chamber View 1. Heart fills one third of the chest  The Four Chamber View 2. Apex points to the left (45 degree angle)  The Four Chamber View 3. Size of right chambers approximates left chambers  The Four Chamber View 4. MV and TV move on real time imaging 5. Ventricular septum symmetric  The Four Chamber View 6. Portion of the atrial septum present Why only a portion?  Left Ventricular Outflow Tract Identify: LV, RV, IV septum, aorta (normal caliber), +/- LA, +/- RA Medial wall of the ascending aorta merges with the top of the IV septum (most frequent location for VSD) Pathology: VSD, tetralogy of Fallot, transposition, truncus arteriosus 54 LVOT 55 Right Ventricular Outflow Tract Identify: branching of the main PA into right PA and ductus arteriosus (to desc Aorta), asc aorta in cross section, desc aorta to left of spine; verify PA crosses anterior to asc aorta Pathology: transposition, truncus arteriosus RVOT 57 Thoracic vessels 58 Ductal Arch/ductus arteriosus  Demonstrates correct orientation and communication between the aorta and the pulmonary trunk  Hockey stick appearance  Arises more anteriorly in the heart  No/neck or head branches 59 How does the fetal diaphragm appear differently than the adult diaphragm? Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 60 Mosby, an The Hepatobiliary System and Upper Abdomen Liver is large organ filling most of upper abdomen Left lobe of liver larger than right lobe because of large quantity of oxygenated blood flowing through left lobe Liver appears pebble-gray; is discerned by its corresponding portal and hepatic vessels 61 The Hepatobiliary System and Upper Abdomen Liver (l, arrows) bordered by the diaphragm (d) superiorly and the bowel inferiorly in a 29-week fetus. 62 The Gastrointestinal System Echogenicity of fetal bowel typically greater than echogenicity of fetal liver If fetal bowel is as echogenic as fetal bone, known as hyperechoic bowel Associated with increased risk for aneuploidy and neonatal/childhood pathology 63  Echogenic bowel Small bowel (arrows) pictured as small fluid- filled rings. b, Bowel; h, heart; s, stomach. Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 64 Mosby, an The Hepatobiliary System and Upper Abdomen Important to check for any collection of fluid around liver margins because this indicates ascites, fluid retention resulting from anemia, heart failure, or congenital anomalies Liver masses uncommon, but may be detected 65 The Hepatobiliary System and Upper Abdomen Fetal gallbladder (GB) appears as cone- shaped or teardrop-shaped cystic structure located in right upper abdomen just below left portal vein GB should not be misinterpreted as left portal vein Left portal vein is midline vessel that appears more tubular and can be traced back to umbilical insertion 66 67 Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 68 Mosby, an The Gastrointestinal System Stomach becomes apparent as early as 11th week of gestation because swallowed amniotic fluid fills stomach cavity Full stomach should be seen in all fetuses beyond 16th week of gestation 69 The Urinary System sonographers required to image and document kidneys and bladder Adrenal glands more prominent in fetus and seen adjacent to kidneys Are apparent as early as 13th week of pregnancy In 2nd trimester of pregnancy, kidneys appear as ovoid retroperitoneal structures that lack distinctive borders 70 The Urinary System Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 71 Mosby, an The Urinary System Measurement of renal pelvis typically made in sagittal view of fetal kidney when fluid present Considered abnormal when: Greater than 5 mm before 20 weeks GA Greater than 8 mm between 20 and 30 weeks GA  Greater than 10 mm beyond 30 weeks GA 72 The Urinary System Fetal adrenal glands most frequently observed in transverse plane just above kidneys Adrenals seen as early as 20th week of pregnancy and by 23 weeks assume rice- grain appearance Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 73 Mosby, an Kidneys vs. Adrenals Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 74 Mosby, an The Urinary System In some normal situations bladder may not be full because of decreased ingestion of fluid When bladder empties in utero, it will typically refill within time frame of examination 75 The Genitalia Providing information regarding gender identification clinically important when fetus at risk for gender-linked disorder like aqueductal stenosis or hemophilia In multiple pregnancies there is medical indication for determining gender as it relates to chorionicity. 76 The Genitalia Female genitalia Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 77 Mosby, an The Genitalia Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 78 Mosby, an The Genitalia 79 The Upper and Lower Extremities Guidelines for standard obstetric examination require sonographer to verify presence or absence of legs and arms Short femur and short humerus associated with increased risk for aneuploidy Sonographer may not only measure fetal limb bones but also survey anatomic configurations of individual bones whenever possible for evidence of bowing, fractures, demineralization, as seen in several common forms of skeletal dysplasia 80 The Upper and Lower Extremities 81 The Upper and Lower Extremities Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 82 Mosby, an The Upper and Lower Extremities Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 83 Mosby, an The Upper and Lower Extremities 84 The Upper and Lower Extremities Hands and fingers may be viewed Note if hands clenched throughout exam or if they open and close normally When fingers viewed in sagittal plane, individual phalanges, interphalangeal joints, metacarpals, and digits may be observed Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 85 Mosby, an The Upper and Lower Extremities Hand movement counts as positive demonstration of fetal tone—one component of biophysical profile Individual fingers can often be counted in first trimester Important to observe hands if anomaly suspected, as in chromosome disorders, such as trisomy 18, in which clenching of hands common 86 The Upper and Lower Extremities Femur is most widely measured long bone; can be found by moving transducer along fetal body to fetal bladder At this junction, iliac wings noted By moving transducer inferior to iliac crests, femoral echo comes into view 87 The Upper and Lower Extremities Longitudinal section showing the femoral shaft (f), with the femoral cartilage (thick arrows) and epiphyseal cartilage (thin arrows) shown at the knee (K). Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 88 Mosby, an The Upper and Lower Extremities Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 89 Mosby, an The Upper and Lower Extremities Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 90 Mosby, an Extra Fetal Obstetric Evaluation After fetus studied, evaluate Placenta Amniotic fluid Pelvis 91 Umbilical Cord  2 arteries, one vein  Absent cord twists may be associated with poor pregnancy outcome  Cord easily imaged in both sagittal and transverse sections  Umbilical vein diameter increases throughout gestation, reaching maximum diameter of 0.9 cm by 30 weeks of gestation 92 Umbilical Cord Identification of placental insertion of cord important in choosing site for amniocentesis and in selection of appropriate site for other invasive procedures Rarely, umbilical insertion atypically located (velamentous insertion) 93 Placenta Cord insert 94 Umbilical Cord Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 95 Mosby, an Abdominal Cord Insert Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 96 Mosby, an Umbilical Cord (sag view) Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 97 Mosby, an Proves three vessel cord- 3VC Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 98 Mosby, an Umbilical Cord Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 99 Mosby, an Umbilical Cord Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 100 Mosby, an Placenta Major role of placenta to permit exchange of oxygenated maternal blood (rich in oxygen and nutrients) with deoxygenated fetal blood Maternal vessels coursing posterior to placenta circulate blood into placenta Blood from fetus reaches this point through the umbilical cord 101 Placenta Copyright © 2012, 2006, 2001, 1995, 1989, 1983, 1978 by 102 Mosby, an Amniotic Fluid Allows fetus to move freely within amniotic cavity Maintains intrauterine pressure and protects developing fetus from injury Umbilical cord and membranes, lungs, skin, and kidneys all contribute to production of amniotic fluid Oligohydramnios – not enough fluid Polyhydramnios – too much fluid 103 Amniotic Fluid 20-week gestation 104 Amniotic Fluid 36-week gestation 105 Membranes Inner membrane, amnion, and outer membrane, chorion, typically not seen during 2nd and 3rd trimesters Amnion contiguous with membrane lining umbilical cord At site of umbilical cord insertion into placenta, amnion spreads out over surfaceCopyright © 2012, of chorionic surface of placenta 2006, 2001, 1995, 1989, 1983, 1978 by 106 Mosby, an Estimation of Fetal Age & Measurements  Estimation of Fetal Age Tools for estimations:  Naegele’s rule:  To determine due date, LMP-3 months + 7 days  Early sonogram with accurate measurements  Compare with previous CRL (most accurate of all) Estimation of Fetal Age: Measurements in the 2nd Trimester Accurate measurement of: BPD, biparietal diameter HC, head circumference AC, abdominal circumference FL, femur length HL, humerus length Additional Measurements  Cerebellum  occipitofrontal diameter (OFD)  Lateral Ventricles  CI (cephalic index)  BIPARIETAL DIAMETER (BPD)  This transverse view of the head includes:  Falx  Thalamus  third ventricle  narrow slit of fluid between the butterfly-shaped paired thalami  cavum septum pellucidum  calipers are placed outer to inner  First measureable between 10 -12 weeks  Angle of asynclitism-sonographically it refers to the angle between the fetal sagittal suture and the central portion of the ultrasound beam.  For an exact BPD, the angle should be 90 degrees.  After 26 weeks, reliability decreases BPD/HC 1. The BPD can be measured through any plane that crosses the 3rd ventricle, thalami, and cavum septi pellucidi (CSP). HC 1. Measurement is through a plane that crosses the 3rd ventricle, thalami, and CSP. 2. The calvaria should be smooth and symmetrical. 3. The cavum septi pellucidi (CSP) should be visible in the anterior portion of the brain. 4. Caliper placement is around the calvarial wall and should not include OCCIPITOFRONTAL (OFD) Outer-to- outer measurement Must be on the same image as the BPD 90 degrees to BPD  Cephalic Index  Defines the shape of the head.  CI = BPD X 100 OFD  Determined by dividing the BPD by the OFD  Normal: 0.7-0.86  In cases of dolichocephaly it will be less than 0.7  In cases of bachycephaly, it will be greater than 0.86.  If it is abnormal, the BPD is eliminated from estimation of Gestational age because it is unreliable HEAD CIRCUMFERENCE, HC Use the same image as the BPD Should not include the scalp, just the skull/calvarium More accurate than BPD when the fetal head is dolichocephalic or brachycephalic Don’t have cerebellum in this image Dolichocephaly  Lateral Ventricles Axial view at the level of the occipital horns and atria of lateral ventricles Measurement is taken by placing calipers across the ventricle at the atria, near the POSTERIOR tip of the choroid plexus, perpendicular to the axis of the lateral ventricle Assess choroid plexus also  Cerebellum, Cisterna Magna @ Axial view of posterior fossa Cerebellum measurement may be useful for GA when you can’t use other measurements Cerebellum/ Cisterna Magna Cerebellum shape and size  Connected by vermis  Transverse cerebellar width (diameter) Cisterna Magna  Normal measurement excludes almost all spinal defects  Siz: normal 2-11 mm, average 5-6 mm 122  Cerebellum/Cisterna Magna Measurement Transverse diameter of the cerebellum is measured at the level of the cerebellar hemispheres CM measured from the vermis to the inner skull ABDOMINAL CIRCUMFERENCE Liver is the largest abdominal organ  Size reflects aberrations of growth, both growth restriction and macrosomia Fetal AC is where the transverse diameter of the liver is the greatest.  ABDOMINAL CIRCUMFERENCE Correct plane is the position with umbilical portion of left portal vein midline within liver (J-shaped curve to right) Measurement is taken along the skin line to include soft tissue and subcutaneous fat Useful in monitoring normal fetal growth and fetal growth disturbances (IUGR) Least accurate for fetal age due to genetic and physiologic variations after 25 weeks.  ABDOMINAL CIRCUMFERENCE If you are in the right place, you will see: -lower ribs, symmetrical - fetal stomach (almost always) -spine, transverse -umbilical vein and portal sinus - adrenal glands, not kidneys (adrenals not always seen) FEMUR LENGTH  From the neck of the femur to the distal end of the femoral condyle NOT to include the epiphysis (seen at 32 wks)  Basically, just measure the ossified part!  FL is less affected by IUGR (Intrauterine Growth Restriction) than the other measurements  Least reliable in establishing gestational age. Why? biologic variability, measurement error  Combination of FL, BPD, & AC are used to determine fetal weight Usually only long bone measured unless there is a > 2 week difference between FL and other parameters. If that is the case, measure all long bones FL Measure from the ends of the ossified femoral diaphysis. Femur Measurement  HUMERUS LENGTH Not as affected by parents’ height as FL Short humerus stronger marker for Down’s Syndrome than short femur If femur and humerus short, measure all long bones to R/O skeletal dysplasia  Humerus Measurement Image fetal spine in upper thoracic—lower cervical region Identify scapula; rotate transducer until long axis of humerus seen Only humeral shaft (diaphysis) ossified and measured; do not include proximal humeral point (PHP) Humerus Measurement  Tibia and Fibula Measurements Tibia longer than fibula Fibula lateral to tibia and thinner Measure length point to point Radius and Ulna Measurements Ulna longer than radius proximally Are the same distally Measure length from point to point Radius and Ulna Measurements  OCULAR MEASUREMENTS Binocular distance: Measured from the lateral orbital rim. May be useful in assessing gestational age in IUGR or when obtaining other measurements is impossible due to fetal position. Fetal Weight Sonography is not a very accurate predictor of absolute weight. It is less accurate the greater the gestational age and even less so in post-term fetuses. Significant variations in weight exist among 3rd trimester fetuses. How it is helpful: Weight changes from serial sonograms can document fetal growth