Basics of early pregnancy scan.pptx

Role of trrans vaginal sonography in early pregnancy as to detect abnormal gestations,early detection of aneuploidies.Study markers for trisomies 13,18,21

1. Basics of early pregnancy scan Poonam Loomba ,M.D.

2. Introduction The main goal of a fetal ultrasound scan is to provide accurate information which will facilitate the delivery of optimized antenatal care with the best possible outcomes for mother and fetus. First trimester’ here refers to a stage of pregnancy starting from the time at which viability can be confirmed (i.e. presence of a gestational sac in the uterine cavity with an embryo demonstrating cardiac activity) up to 13 + 6 weeks of gestation.

3. Objectives 1. Highlight embryonic developmental features. 2. Application of TVS in management of early pregnancy failure ,ectopic pregnancy and multiple pregnancies. 3. Placental pathologies on USG. 4.To identify and evaluate first trimester markers of aneuploidy 5. 3D and 4D USG in first trimester 6.Markers for Preeclampsia through TVS in Early pregnancy. Few interesting cases.

4. We use the term ‘embryo’ for before 10 weeks and ‘fetus’ thereafter, to reflect the fact that after 10 weeks of gestation organogenesis is essentially complete and further development involves predominantly fetal growth and organ maturation.

5. When should you perform scan It is advisable to offer the first ultrasound scan when gestational age is thought to be between 11 and 13 + 6 weeks’ gestation. Before starting the examination, a healthcare provider should counsel the woman/couple regarding the potential benefits and limitations of the first-trimester ultrasound scan.

6. Is prenatal ultrasonography safe during the first trimester? B-mode and M-mode prenatal ultrasonography , due to its limited acoustic output, appears to be safe for all stages of pregnancy . Doppler ultrasound is however, associated with greater energy output and therefore more potential bioeffects , especially when applied to a small region of interest. Doppler examinations should only be used in the first trimester, therefore, if clinically indicated.

7. Gestation sac The MSD is the average of the three orthogonal measurements of the fluid-filled space within the gestational sac. The size threshold for sac detection is 2 to 3mm corresponding to between 4 weeks 1 day to 4 weeks 3 days gestation The loss rate at this stage is 11.5 %

8. Position of GSAC Normal position is in the mid to upper uterus Intradecidual sign :as the sac implants into the decidualized endometrium it should be adjacent to linear central cavity echo complex without displacing this hyperechoic anatomic landmark Double decidual sac sign : as the sac enlarges it impresses and deforms the central cavity echo complex giving appearance of DDSS .Visible when MSD is 10mm. DDS

9. The use of terms such as an ‘apparently empty’ sac, the Double decidual ring’ or even ‘ pseudosac ’ do not accurately confirm or refute the presence of an intrauterine pregnancy. In an asymptomatic patient, it is advisable to wait until the embryo becomes visible within the intrauterine sac as this confirms that the ‘sac’ is indeed a gestational sac. pregnancy.

10. Abnormal gestation sacs Transvaginal sonographic diagnosis of a blighted ovum is certain when the mean gestational sac diameter exceeds 8mm without a yolk sac or when the mean gestational sac diameter exceeds 16 mm without an embryo Transabdominally, a gestational sac greater than 20 mm without a yolk sac or 25 mm without an embryo is diagnostic of a blighted ovum

11. Trophoblastic appearance Distorted sac shape thin<2mm weakly echogenic and irregular choriodecidual reaction Absence of DDSC when MSD>10 mm Presence of chorionic bump(irregular convex bulge arising from choriodecidual surface and protruding into GSAC)

12. Small sac size growth delay A small sac size relative to the embryo (difference of less than 5 mm between gestational sac and crown/rump length) indicates early oligohydramnios and increased rate of abortion

13. Identifying yolk sac The yolk sac is seen by transvaginal ultrasound when the mean gestational sac diameter is 5 to 6 mm(5 weeks) and should always be visualized when the mean gestational sac diameter is greater than or equal to 8 mm.(5.5 weeks )

14. Yolk sac Yolk sac is normally spherical in shape with a well defined echogenic periphery and a sonoluscent centre Size :steadily increases from 5 to 10 weeks to a max of 5 to 6mm(corresp to CRL 30 to 45 mm) As GA advances it seperates and detatches from the embryo,diameter decreases and becomes irregular Not visualized on tvs by end of first trimester

15. Yolk sac abnormalities E nlarged (5 to 6 mm) seen in IDDM or abnormally shaped (crenellated) yolk sac, Calcified Echogenic Double yolk sac

16. Identifying the embryo The embryo can be identified by transvaginal ultrasound when as small as 1 to 2 mm in length(corresponding to 5 to 6 weeks GA and MSD between 5 to 12mm) Its seen as a focal area of thickening along the periphery of yolk sac At 5 to 7 weeks, both the embryo and gestational sac should grow by 1 mm daily.

17. Viability Cardiac activity is often evident when the embryo measures 2 mm or more but is not evident in around 5–10% of viable embryos measuring between 2 to 4 mm. From 5.5 to 6.5 weeks, an embryonic heart rate of less than 100 beats per minute is normal. During the following 3 weeks, there is a rapid increase up to 180 beats per minute.

18. Normal Heart Rate 5.5 to 6 wks : 1. 100-125/min 2. <100/min 3 100 -115/min 8wks and above 1. 137-144/min 2 144-159/min 3 140 -160/min

19. CARDIAC ACTIVITY ABSENT Sonographic diagnosis of embryonic demise can be made when there is no cardiac activity in an embryo greater than 5mm by transvaginal ultrasound or 9 mm by abdominal ultrasound (If cardiac activity is present in at 8 weeks the risk of loss is only 2 to 3%)

20. Predictors of early pregnancy loss Heart rate- Persistent bradycardia (heart rate less than 100BPM at 6.5 weeks and less than 120 between 6.5 and 7 weeks of gestation,) Bradycardia associated with triploidy and trisomy 18 Tachycardia associated with trisomy 13 and turners syndrome

21. Transformation in the structure of embryo During 6 th week,with ventral folding of cranial and caudal ends of embryo it changes shape from a flat disc to a 3d C shaped structure Brain and head become prominent as rostral neuropore closes and caudal neuropore elongates and curves into a tail

22. By 7 th to 8 th week limb buds evolve By 9 th week extremities protrude ventrally trunk elongates and straightens and midgut herniation into umbilical cord becomes more prominent By 10 th week at embryo length 30 mm to 35 mm human appearing embryo is seen

23. Assessment of gestational age Pregnant women should be offered an early ultrasound scan between 10 + 0 and 13 + 6 weeks to establish accurate gestational age. (Grade A recommendation) In the first trimester, many parameters are related closely to gestational age, but CRL appears to be the most precise allowing accurate determination of the day of conception, to within 5 days either way in 95% of cases.

24. If pregnancy resulted from assisted reproductive technology (ART), the ART-derived gestational age should be used to assign the estimated due date (EDD). 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.

25. Measuring CRL CRL measurements can be carried out transabdominally or transvaginally. A midline sagittal section of the whole embryo or fetus should be obtained, ideally with the embryo or fetus oriented horizontally on the screen. An image should be magnified sufficiently to fill most of the width of the ultrasound screen, so that the measurement line between crown and rump is at about 90 degrees to the ultrasound beam Electronic linear calipers should be used to measure the fetus in a neutral position (i.e. neither flexed nor hyperextended. ) Care must be taken to avoid inclusion of structures such as the yolk sac. In order to ensure that the fetus is not flexed, amniotic fluid should be visible between the fetal chin and chest

26. 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 Mean sac diameter measurements are not recommended for estimating the due date. It is recommended that CRL measurement should be used to determine gestational age unless it is above 84 mm; after this stage, HC can be used, as it becomes slightly more precise than is BPD. (GOOD PRACTICE POINT)

27. Note true axial view through head and central position of third ventricle and midline structures (T indicates third ventricle and thalamus). Head circumference would also be measured in this plane.

28. Normal choroid plexuses (C) and midline falx and interhemispheric fissure (arrows). Note that choroid plexuses extend from the medial to the lateral border of the posterior horn. Lateral walls of anterior horns are indicated by arrowheads.

29. Doppler can be helpful in confirming the presenceof two umbilical arteries, but this is not part of the routine assessment.

30. Axial section of the fetal thorax at the level of the four-chamber view of the heart, with the cardiac apex pointing to the left (L). Note atria and ventricles are symmetrical on either side of the septum (arrow). Lung fields are of homogeneous Echogenicity and symmetrical. Aorta is just to left side of spine (S).

31. Fetal spine. Intact skin is visible posterior to the vertebrae from neck to sacrum in a true median view. Note vertebral bodies show ossification, but neural arches, which are still cartilaginous, are isoechoic or hypoechoic .

32. Face with lips,nostrils

33. Nuchal Translucency Needs high standard of knowledge and expertise. The machine should have a good resolution ,video loop function . In 95% of cases it can be measured by TAS ..in rest by TVS. Minimum 80-100 scans needed for good results.

34. PROTOCOL FOR MEASURING NT Fetus in neutral position. Mid sagittal plane with face and chest occupying full screen 11 to 13+ 6 weeks The magnification should be such that each increment in the distance between calipers should be 0.1mm

35. NT Measurements should be taken with the inner border of the horizontal line of the callipers placed ON the line that defines the nuchal translucency thickness - the crossbar of the calliper should be such that it is hardly visible as it merges with the white line of the border, not in the nuchal fluid. In magnifying the image (pre or post freeze zoom) it is important to turn the gain down. This avoids the mistake of placing the calliper on the fuzzy edge of the line which causes an underestimate of the nuchal measurement. During the scan more than one measurement must be taken and the maximum one that meets all the above criteria should be recorded in the database.

36. NT

37. . The umbilical cord may be round the fetal neck in about 5% to 10% of cases and this finding may produce a falsely increased NT. In such cases, the measurements of NT above and below the cord are different and, in the calculation of risk, it is more appropriate to use the lowest of the two measurements

38. Causes of increased NT Aneuplodies Abnormalities of heart and great arteries Amnion rupture Diaphragmatic hernia Skeletal dysplasias Achondrogenesis Hypoplasia of lymhatics as in Turner syndrome. Anaemia Congenital infections

39. Screening for chromosomal anamolies using NT involves: 1 . Carrying out the ultrasound examination by appropriately trained sonographers. 2.Measurement of maternal serum free β-hCG and PAPP-A by laboratories that can demonstrate good quality assurance performance. 3. A risk calculation program that uses an algorithm based on scientific evidence. 4 Appropriate counselling of the parents.

40. USG Parameters for detection of downs syndrome in first trimester Nuchal translucency Nasal bone(absent 69% cases) FMF angle Ductus venosus flow velocity waveform Tricuspid regurgitation Fetal heart rate(tachycardia) Underdevelopment of maxilla(seen in 50% cases) Short ear length Short femur and humerus during 11-16 weeks at 6 day scan window

41. USG Parameters for detection of Trisomy 13 in first trimester Nuchal translucency Nasal bone(absent 40% cases) Fetal facial angle(increased 45% cases) Ductusvenosus Tricuspid regurgitation Megacystis(urinary bladder length >7mm)20% Fetal tachycardia

42. Trisomy 18 Trisomy 18: absent nasal bone 50% cases,single umbilical artery(7 fold ),fetal bradycardia Turners syndrome:choroid plexus cyst(75% cases)

43. NASAL BONE EVALUATION In a high proportion of fetuses with trisomy 21 and other chromosomal abnormalities the nasal bone is hypoplastic or not visible at 11-13 weeks' gestation. Assessment of the nasal bone at 11-13 weeks improves the performance of combined screening for trisomy 21 by maternal age, fetal nuchal translucency (NT) and serum biochemistry. The difficulty is when the gestation is 11 weeks or the beginning of the 12th week and the nasal bone is absent but the NT, the other ultrasound markers and the serum biochemistry are normal.

44. PROTOCOL The gestational period must be 11 to 13 weeks and six days. The magnification of the image should be such that the fetal head and thorax occupy the whole image. A mid-sagittal view of the face should be obtained. This is defined by the presence of the echogenic tip of the nose and rectangular shape of the palate anteriorly, the translucent diencephalon in the centre and the nuchal membrane posteriorly. Minor deviations from the exact midline plane would cause non-visualization of the tip of the nose and visibility of the zygomatic process of the maxilla.

45. How to measure NB The ultrasound transducer should be held parallel to the direction of the nose and should be gently tilted from side to side to ensure that the nasal bone is seen separate from the nasal skin. The echogenicity of the nasal bone should be greater that the skin overlying it. In this respect, the correct view of the nasal bone should demonstrate three distinct lines: the first two lines, which are proximal to the forehead, are horizontal and parallel to each other, resembling an "equal sign". The top line represents the skin and bottom one, which is thicker and more echogenic than the overlying skin, represents the nasal bone. A third line, almost in continuity with the skin, but at a higher level, represents the tip of the nose.

46. When the nasal bone line appears as a thin line, less echogenic than the overlying skin, it suggests that the nasal bone is not yet ossified, and it is therefore classified as being absent.

47. Three-dimensional (3D) and 4D ultrasound are not currently used for routine first-trimester fetal anatomical evaluation, as their resolution is not yet as good as that of 2D ultrasound. In expert hands, these methods may be helpful in evaluation of abnormalities, especially those of surface anatomy. Role of 3D/4D

48. Intrauterine blood Presence of subchorionic blood increases the abortion rate to 8 % Various sites are:retroplacental Preplacental Marginal Subamniotic On USG it appears initially as a hypoechoic area adjacent to GSAC which later becomes hypo/anechoic

49. Subchorionic haemorrhage

50. Amnion abnormailities Membrane is easily visualized Thickness and echogenicity similar to yolk sac Enlarged yolk sac in relation to CRL(normal preg diff 1mm in CRL and amniotic cavity diameter) Double bleb sign

51. Role of doppler in predicting poor pregnancy outcome Elevated resistance in uterine and subchorionic vessels increase abortion rate Increased corpus luteal RI- increased preg loss

52. DIAGNOSING MULTIPLE PREGNANCY Always begin a scan with a complete imaging sweep of the uterus and count the number of fetus, determine their presentation,document their site and chorionicity First trimester evaluation is the best time to determine the chorionicity in multiple gestation

53. Chorionicity assessment (before 10 weeks) Number of Yolk Sacs Number of GSAC Number of amniotic sacs in chorionic cavity

54. After 10 weeks Sex discordance No of distinct placenta Twin peak/lambda sign-results from echodense chorionic villi between the two layers of chorion at its origin from the placenta.(100% PPV for DC placentation) T sign:MCMA placentation Epsilon sign:TCTA placentation Membrane thickness:cutoff 2mm

55. Peak

56. USG features of ectopic pregnancy The sonographic appearance of an ectopic is varied ranging from simple adnexal cyst, complex adnexal mass, tubal ring, (ring on fire app) free fluid in the adnexa-cul de sac, a live extrauterine fetus, or an empty uterus with no other sonographic findings

57. USG features for ectopic Negative sonographic signs -intrauterine pregnancy False negative sonographic sign -intrauterine Gsac Indirect positive sign -empty uterus and the discriminatory zone and free pelvic and abdominal fluid Direct positive sign -adnexal pregnancy,tubal or adnexal ring,complex or solid mass

58. Placental pathologies Echo rich trophoblastic tissue-diffuse small cystic structures without gestational components. Snowstorm appearance Theca lutein cysts in adnexal region(soap bubble or spoke wheel app of ovaries)

59. Placental pathologies Echo rich trophoblastic tissue-diffuse small cystic structures without gestational components. Snowstorm appearance Theca lutein cysts in adnexal region(soap bubble or spoke wheel app of ovaries)

60. Diagnosing anomalies(excluding nt) Anencephaly Large encephalocoels Holoprosencephaly Cystic hygroma Omphalocoel/gastrochisis(size of protruding ant abd mass>7mm and persistence beyond 12weeks) Amniotic band syndrome Conjoined twins

61. DUCTUS VENOSUS FLOW Increased impedance to flow in the fetal ductus venosus at 11-13 weeks’ gestation, is associated fetal aneuploidies, cardiac defects and other adverse pregnancy outcomes. Most studies examining ductus venosus flow have classified the waveforms as normal, when the a-wave observed during atrial contraction is positive, or abnormal, when the a-wave is absent or reversed. The preferred alternative in the estimation of patient-specific risks for pregnancy complications is measurement of the pulsatility index for veins (PIV) as a continuous variable.

62. PROTOCOL The gestational period must be 11 to 13 weeks and six days. The examination should be undertaken during fetal quiescence. The magnification of the image should be such that the fetal thorax and abdomen occupy the whole image. A right ventral mid-sagittal view of the fetal trunk should be obtained and color flow mapping should be undertaken to demonstrate the umbilical vein, ductus venosus and fetal heart. The pulsed Doppler sample volume should be small (0.5-1.0 mm) to avoid contamination from the adjacent veins, and it should be placed in the yellowish aliasing area. The insonation angle should be less than 30 degrees.

63. TRICUSPID FLOW Tricuspid regurgitation at 11-13 weeks’ gestation is a common finding in fetuses with trisomies 21, 18 and 13 and in those with major cardiac defects. Tricuspid regurgitation is found in about 1% of euploid fetuses, in 55% of fetuses with trisomy 21 and in one third of fetuses with trisomy 18 and trisomy 13. Inclusion of tricuspid blood flow in first-trimester combined screening improves the detection rate for trisomy 21 from about 90% to 95% for a false positive rate of 3%. Assessment of tricuspid flow need not be carried out in all pregnancies undergoing routine first-trimester combined screening. Such examination could be reserved for the 15% of the total population with an intermediate risk (between 1 in 51 and 1 in 1000) after combined testing.

64. PROTOCOL The gestational period must be 11 to 13 weeks and six days. The magnification of the image should be such that the fetal thorax occupies most of the image. An apical four-chamber view of the fetal heart should be obtained. A pulsed-wave Doppler sample volume of 2.0 to 3.0 mm should be positioned across the tricuspid valve so that the angle to the direction of flow is less than 30 degrees from the direction of the inter-ventricular septum.

65. Tricuspid regurgitation Tricuspid regurgitation is diagnosed if it is found during at least half of the systole and with a velocity of over 60 cm/s, since aortic or pulmonary arterial blood flow at this gestation can produce a maximum velocity of 50 cm/s. The sweep speed should be high (2-3 cm/s) so that the waveforms are widely spread for better assessment. The tricuspid valve could be insufficient in one or more of its three cusps, and therefore the sample volume should be placed across the valve at least three times, in an attempt to interrogate the complete valve.

66. PREECLAMPSIA SCREENING There is now evidence that a combination of maternal demographic characteristics, including medical and obstetric history, uterine artery pulsatility index (PI), mean arterial pressure (MAP) and maternal serum pregnancy associated plasma protein-A (PAPP-A) and placental growth factor (PlGF) at 11-13 weeks' gestation can identify a high proportion of pregnancies at high-risk for PE. Such early identification of the high-risk group for PE is important because the risk may be substantially reduced by the prophylactic use of low-dose aspirin starting from 11-13 weeks.

67. PROTOCOL FOR MEASURING UTERINE A PI The gestational age must be between 11 weeks and 13 weeks and six days. Sagittal section of the uterus must be obtained and the cervical canal and internal cervical os identified. Subsequently, the transducer must be gently tilted from side to side and then colour flow mapping should be used to identify each uterine artery along the side of the cervix and uterus at the level of the internal os. Pulsed wave Doppler should be used with the sampling gate set at 2 mm to cover the whole vessel and ensuring that the angle of insonation is less than 30º. When three similar consecutive waveforms are obtained the PI must be measured and the mean PI of the left and right arteries be calculated.

68. Other intra- and extrauterine structure Special attention should be given to patients with a prior Cesarean section, who may be predisposed to scar pregnancy or placenta accreta , with significant complications. The uterine isthmus at the site of the Cesarean section scar should be scrutinized. In suspected cases, consideration should be given to prompt specialist referral for further evaluation and management. Although the issue of routine scans in women with a history of Cesarean section may be raised in the future There is currently insufficient evidence to support inclusion of such a policy in routine practice.

69. Gynaecological conditions Gynecological pathology, both benign and malignant, may be detected during any first-trimester scan. Abnormalities of uterine shape, such as uterine septa and bicornuate uteri, should be described. The adnexa should be surveyed for abnormalities and masses.

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