Ultrasound

Embryology - 1 Dec 2023        Expand to Translate
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Introduction

Ultrasound Imaging planes

The generic term ultrasound refers to the non-invasive technique using sound waves in the ultrasonic (above our hearing range) frequency. The technique can visualise and allow prenatal diagnosis of several features of development of: follicles in the ovary, the gestational sac, fetus in the uterus, fetal parameters, and the placenta. Ultrasound imaging began in the 1950's but it was only with the application of computer analysis beginning in the 1980's that more detailed images could be generated. This current page links to all human and animal ultrasound movies, you can also use the Category:Ultrasound to find related content.

Parents now commonly see ultrasound movies or images in the first trimester and clinically this is a non-invasive prenatal diagnostic tool for detection of abnormalities as well as a method of staging (ageing) and checking growth. There are several different standards available for calculating age based upon several measurements, including embryo or fetal crown rump length (CRL).

Ultrasound can also be used in combination with other techniques to locate both embryo and placenta for other prenatal tests (More? prenatal diagnosis). Development of modern ultrasound techniques now allow the measurement of blood flow (doppler) as well as computer three-dimensional reconstruction of embryos or structures.

The ultrasound technique can be used at any stage during pregnancy for fetal and placenta monitoring (More? placenta | Placenta Abnormalities | Prenatal Diagnosis).

Some diagnostic measurements include:

• Trisomies - Nuchal translucency (NT), nasal bone visualization (NB)
• Cardiovascular - tricuspid valve regurgitation (TR), "a"-wave pattern, DV PIV, S-wave (peak systolic velocity), D-wave (peak diastolic velocity), a-wave (atrial contraction in late diastole), time-averaged maximum velocity (TAMXV)

How to Play Ultrasound Movies
<html5media height="300" width="400">File:Ultrasound_Fetus_02.mp4</html5media>	The ultrasound movies can be viewed in two ways: Clicking either the movie image or "Page" text below the image opens a new page with both the movie and a more detailed text description of features. Embedded movies then play by clicking the play triangle icon lying over the movie image. Clicking on the "Play" link will open the MP4 movie version alone on a new page. Abnormal developmental ultrasound and features are listed on a separate page (More? abnormal ultrasound) all content is for educational use only.
Page | Play Movie shows a 12 week fetus in 3d in realtime (hence 4D).	Special thanks to Dr Andrew McLennan, Foetal Medicine Unit, Royal North Shore Hospital and Dr Stanley Ng for many of the original video materials.

| Abnormal Ultrasound

Some Recent Findings

Diagnosing Small for Gestational Age during second trimester routine screening: Early sonographic clues "Small for gestational age (SGA) is generally defined as birth weight being at or below the 10th percentile. Children with SGA have a higher risk for complications. There is a need for early predictors, as the accurate diagnosis rate is only 50%. In the current study, we aimed to evaluate diagnostic performance of ultrasound (US)/color Doppler ultrasound (CDUS) parameters (umbilical vein-UV, right portal vein-RPV diameter/flow rate, and portal sinus-PS diameter) examined at 20-22 gestational week as SGA diagnostic factors. UV, RPV, and PS diameters can be earlier predictors for SGA diagnosis. Routinely evaluation of these parameters during second trimester screening can increase SGA diagnosis rates and serve for early diagnose." Longitudinal Doppler references for monochorionic twins and comparison with singletons "To construct monochorionic (MC) twin-specific longitudinal doppler ultrasound references for umbilical artery pulsatility index (UA-PI), middle cerebral artery (MCA) PI and peak systolic velocity (PSV) and ductus venosus (DV) PI derived from a strictly selected cohort of uncomplicated MC twins. The secondary aim of the study was to compare our findings with singleton reference charts. The study group comprised 150 uncomplicated MC twin pairs. Estimated centiles (3rd, 5th, 10th, 50th, 90th, 95th, 97th) of UA-PI, MCA-PI, MCA-PSV and DV-PI in function of the gestational age are presented. The comparison with singletons showed substantial differences, with higher UA-PI and lower MCA-PI and PSV median values in MC twins. Median DV PI values were similar to the values for singletons, while the upper centiles were higher in MC twins." twinning Sensitivity of prenatal ultrasound for detection of Trisomy 18 "To evaluate the sensitivity of prenatal ultrasound (US) for trisomy (T18) diagnosis and describe US findings in a large tertiary care institution in the USA. Materials and methods: This was a retrospective cohort of all T18 cases diagnosed at our institution from October 2004 to October 2014 based on prenatal or postnatal genetic diagnostic testing. We included all women with a fetus affected by T18 who had a comprehensive US by a maternal-fetal medicine specialist performed at our institution. US findings were reviewed, classified by organ system, and categorized as an anomaly or soft marker. Chi-square or t-test was used for statistical analysis. Results: We included 128 cases of T18 with confirmed cytogenetic analysis -110 (86%) of which were diagnosed prenatally or suspected by cell-free DNA and confirmed postnatally, and 18 of which underwent neonatal blood sampling alone. One hundred and twenty-one (95%) had at least one abnormal US finding. Anomalies were more frequently identified on US at ≥20 weeks as compared with <20 weeks (93% versus 76%; p = .004). The mean number of findings detected per fetus was 5.1 ± 3.0. Fetuses diagnosed by postnatal sampling alone had a similar number of US exams performed and number of abnormal findings compared to those diagnosed prenatally. Conclusion: Ninety-five percent of fetuses with T18 had at least one abnormal US finding. This sensitivity of is higher than reported in most prior studies, but is not 100%, and should be considered when counseling women regarding prenatal diagnosis of T18. Rationale: Historical detection rates for abnormal sonographic findings in trisomy 18 fetuses range from 70% to 100%. These studies are limited by small sample sizes. This is a contemporary study of ultrasound findings in a large group of women with confirmed trisomy 18 by prenatal or postnatal genetic diagnosis. We provide expansive detail on soft markers and anomalies broken down by organ-system and gestational age." Subarachnoid space diameter in chromosomally abnormal fetuses at 11-13 weeks' gestation "To examine the subarachnoid space diameters in chromosomally abnormal fetuses at 11-13 weeks' gestation. Stored three-dimensional (3D) ultrasound volumes of the fetal head at 11-13 weeks' gestation from 407 euploid and 88 chromosomally abnormal fetuses (Trisomy 21, n = 40; Trisomy 18, n = 19; Trisomy 13, n = 7; triploidy, n = 14; Turner syndrome, n = 8) were analyzed. The subarachnoid space diameters, measured in the sagittal and transverse planes of the fetal head, in relation to biparietal diameter (BPD) in each group of aneuploidies was compared to that in euploid fetuses. A total of 20 head volumes were randomly selected and all the measurements were recorded by two different observers to examine the interobserver variability in measurements. In euploid fetuses, the anteroposterior, transverse and sagittal diameters of the subarachnoid space increased with BPD. The median of the observed to expected diameters for BPD were significantly increased in triploidy and Trisomy 13 but were not significantly altered in Trisomy 21 and Trisomy 18 or Turner syndrome. In triploidy, the subarachnoid space diameters for BPD were above the 95th centile of euploid fetuses in 92.9% (13 of 14) cases. The intraclass reliability or agreement was excellent for all three subarachnoid space diameters. Most fetuses with triploidy at 11-13 weeks' gestation demonstrate increased subarachnoid space diameters." ventricular

More recent papers

This table allows an automated computer search of the external PubMed database using the listed "Search term" text link. This search now requires a manual link as the original PubMed extension has been disabled. The displayed list of references do not reflect any editorial selection of material based on content or relevance. References also appear on this list based upon the date of the actual page viewing. References listed on the rest of the content page and the associated discussion page (listed under the publication year sub-headings) do include some editorial selection based upon both relevance and availability. More? References | Discussion Page | Journal Searches | 2019 References | 2020 References Search term: Fetal Ultrasound | First Trimester Ultrasound | Second Trimester Ultrasound | Fetal Doppler Ultrasound |

Older papers

These papers originally appeared in the Some Recent Findings table, but as that list grew in length have now been shuffled down to this collapsible table. See also the Discussion Page for other references listed by year and References on this current page. Diagnosis of Fetal Structural Anomalies at 11 to 14 Weeks "To assess the performance of first-trimester ultrasound (US) in identifying major fetal structural abnormalities in an unselected population. ...In the first trimester, we identified 79% of all major structural anomalies. The highest detection rates were achieved for abdominal wall defects (100%), major central nervous system anomalies (88%), cardiac defects (74%), and skeletal anomalies (71%). The nuchal translucency was increased in 35% of the cases with structural anomalies, and 95% of these were diagnosed in the first trimester." Dating of Pregnancy in First versus Second Trimester in Relation to Post-Term Birth Rate: A Cohort Study "To evaluate in a national standardised setting whether the performance of ultrasound dating during the first rather than the second trimester of pregnancy had consequences regarding the definition of pre- and post-term birth rates. A cohort study of 8,551 singleton pregnancies with spontaneous delivery was performed from 2006 to 2012 at Copenhagen University Hospital, Holbæk, Denmark. We determined the duration of pregnancy calculated by last menstrual period, crown rump length (CRL), biparietal diameter (1st trimester), BPD (2nd trimester), and head circumference and compared mean and median durations, the mean differences, the systematic discrepancies, and the percentages of pre-term and post-term pregnancies in relation to each method. The primary outcomes were post-term and pre-term birth rates defined by different dating methods. ...Systematic discrepancies were identified when biometric formulas were used to determine duration of pregnancy. This should be corrected in clinical practice to avoid an overestimation of post-term birth and unnecessary inductions when first trimester formulas are used." Uterine Doppler velocimetry of the uterine arteries in the second and third trimesters for the prediction of gestational outcome "The aim of this longitudinal study was to investigate the value of uterine artery Doppler sonography during the second and third trimesters in the prediction of adverse pregnancy outcome in low-risk (205 singleton pregnant) women. ...The uterine artery PI and RI values for both second and third-trimester evaluations were significantly higher in patients with adverse pregnancy outcome than in normal women." doppler ultrasound | placental cord 13-14-week fetal anatomy scan: a 5-year prospective study "To assess the potential value of an early (first-trimester) ultrasound examination in depicting fetal anomalies by transabdominal (TAS) and transvaginal (TVS) sonography, to compare it with the traditional mid-trimester anomaly ultrasound examination and to evaluate the degree of patient acceptance of early sonography by the transvaginal route. ...TVS was significantly better in visualizing the cranium, spine, stomach, kidneys, bladder and upper and lower limbs (P < 0.001). Complete fetal anatomical surveys were achieved by TAS in 64% of cases versus 82% of the cases in which it was attempted by TVS (P < 0.001). ...Besides its importance in screening for chromosomal abnormalities, the early scan has great potential in visualizing with precision fetal anatomy. TVS can be used to compliment difficult TAS examinations; however, patients do not always agree to undergo TVS. The mid-trimester scan remains crucial for detailed fetal anatomical survey." Comparison between ultrasound and magnetic resonance imaging in assessment of fetal cytomegalovirus infection "MRI can provide important additional information with regard to abnormal gyration, cerebellar hypoplasia, or abnormal signal in white matter. It is certainly useful in the assessment of fetuses with extracerebral features without brain abnormalities detected with ultrasounds. If the fetal ultrasound is strictly normal in an infected fetus, MRI may not detect brain anomalies; however, it seems difficult to not perform this noninvasive procedure." Prenatal diagnosis of vasa previa through color Doppler and three-dimensional power Doppler ultrasonography "Vasa previa occurs in pregnancy when one of the membrane vessels extends down to the level of the internal cervical os, ahead of the fetal presenting part and unsupported by the placenta tissue or umbilical cord. The rupture of the vessels might happen spontaneously or artificially and frequently results in fetal exsanguination and demise. Ultrasound prenatal diagnosis is highly important as it allows the identification of patients at risk, thus an elective cesarean can be performed before rupture the membranes. We report a case of vasa previa diagnosed through color Doppler mode in the 30th week of gestation, emphasizing the contribution of three-dimensional power Doppler to the adequate mapping of aberrant vessels, which greatly contributed to the success of the perinatal result."

Ultrasound Movies

This table of images links to both normal and abnormal ultrasound movies. Page link will open a new window with the movie and additional information.

Normal Ultrasound  ‎‎Ultrasound 12wk Page | Play ‎‎12 Week Heart Rate Page | Play  ‎‎19 Week Fetus Page | Play     ‎‎Rabbit Embryo Page | Play Ultrasound: normal movies | abnormal movies | all ultrasound movies | Movies

Abnormal Ultrasound Uterus Cleft Lip  ‎‎Ectopic Pregnancy Page | Play  ‎‎Bicornuate Ectopic Page | Play  ‎‎Cleft Lip 18 Week Page | Play  ‎‎Cleft Lip 15 Week Page | Play Gastrointestinal Neural  ‎‎Gastroschisis Page | Play  ‎‎Omphalocele Page | Play  ‎‎Dandy-Walker Page | Play  ‎‎Spina Bifida Page | Play Cardiac  ‎‎Heart TGA Page | Play  ‎‎Hypoplastic Left Heart Syndrome Page | Play  ‎‎Patent Ductus Venosus Page | Play Placenta  ‎‎Placenta Previa Page | Play  ‎‎Vasa Previa Page | Play  ‎‎Velamentous Cord Page | Play Ultrasound: normal movies | abnormal movies | all ultrasound movies | Movies

Ultrasound Gestational Age

The following table is based upon Australian data from ultrasound measurements of Crown Rump Length (CRL).

Note that Gestational Age GA differs from fertilisation age by about 2 weeks.

Gestational Age and Crown-Rump Length (measured by ultrasound)

Gestational Age GA (week.day) Crown-Rump Length (CRL) 5.2 1 5.3 2 5.4 3 55 3 5.6 4 6 4 6.1 5 6.2 6 6.3 7 6.4 8 6.5 9 6.6 10 7 11 7.1 11 7.2 12 7.3 12 7.4 13 7.5 14 7.6 15 8 17 8.1 18 8.2 19 8.3 20 8.4 21 8.5 22 8.6 22 9 23 9.1 24 9.2 26 9.3 27 9.4 28 9.5 29 9.6 31 10 34 10.1 36 10.2 37 10.3 38 10.4 39 10.5 39 10.6 40 11 44 11.1 45 11.2 47 11.3 48 11.4 52 11.5 55 11.6 56 12 57 12.1 58 12.2 60 12.3 61 12.4 63 12.5 64 12.6 65 13 68 13.1 70 13.2 72 13.3 74 113.4 76 135 77 13.6 80 14 81 14.1 84 14.2 85 14.3 86 14.4 87 Reference Table adapted from Westerway (2015) PDF and <pubmed>11065037</pubmed>

Fertilization and Gestational Age - Crown-Rump Length (ultrasound)

Fertilization Age (days) Gestational Age GA (week.day) Crown-Rump Length (mm) 37 5.2 1 38 5.3 2 39 5.4 3 40 55 3 41 5.6 4 42    Week 4 6 4 43 6.1 5 44 6.2 6 45 6.3 7 46 6.4 8 47 6.5 9 48 6.6 10 49    Week 5 7 11 50 7.1 11 51 7.2 12 52 7.3 12 53 7.4 13 54 7.5 14 55 7.6 15 56    Week 6 8 17 57 8.1 18 58 8.2 19 59 8.3 20 60 8.4 21 61 8.5 22 62 8.6 22 63    Week 7 9 23 64 9.1 24 65 9.2 26 66 9.3 27 67 9.4 28 68 9.5 29 69 9.6 31 70    Week 8 10 34 71 10.1 36 72 10.2 37 73 10.3 38 74 10.4 39 75 10.5 39 76 10.6 40 77    Week 9 11 44 78 11.1 45 79 11.2 47 80 11.3 48 81 11.4 52 82 11.5 55 83 11.6 56 84    Week 10 12 57 85 12.1 58 86 12.2 60 87 12.3 61 88 12.4 63 89 12.5 64 90 12.6 65 91    Week 11 13 68 92 13.1 70 93 13.2 72 94 13.3 74 95 113.4 76 96 135 77 97 13.6 80 98    Week 12 14 81 99 14.1 84 100 14.2 85 101 14.3 86 102 14.4 87 Reference: Table data measured by ultrasound, adapted from Westerway (2015) PDF and Links: ultrasound | Fetal Development

CRL-GA TableFA-GA-CRL

First Trimester Ultrasound

First trimester screening refers to the ltrasound scan typically carried out between GA 11^{+ 0} – 13^{+ 6} weeks. The scan can determine the gestation age GA, embryo anatomical size measurements, placenta position and structure.

The scan can also detect, with varying degrees of accuracy, some developmental abnormalities.

Detectable

• anencephaly/exencephaly
• holoprosencephaly
• omphalocele gastroschisis
• body stalk anomaly
• megacystis

Potentially Detectable

• hand and foot abnormalities
• diaphragmatic hernia
• lethal skeletal dysplasia
• severe heart defects
• spina bifida aperta
• facial clefts

Not Detectable

• microcephaly
• anomaly of the corpus callosum
• ventriculomegaly
• tumors
• ovarian cysts
• pulmonary lesions
• gastrointestinal obstructions

Second Trimester Ultrasound

Second trimester ultrasound provides information about: number of fetuses, gestational age, location of the placenta, fetal growth and maternal anatomy.

Doppler Ultrasound

Doppler ultrasound is a noninvasive measure of blood flow and blood pressure by bouncing ultrasound off circulating red blood cells. Originally used for fetal heart beat detection, more recently used diagnostically in uterine, placental, ductus venosus and other fetal blood vessels.

Doppler effect is due to the movement of blood cells causing a change in pitch of the reflected sound waves.

Velamentous Cord Insertion	Vasa Previa
<html5media>File:Velamentous cord insertion 02.mp4</html5media> This colour doppler ultrasound movie shows blood flow in the umbilical cord inserted into the post uterine wall and then courses superiorly to enter the fundal edge of the anterior placenta.	‎‎Vasa Previa Page | Play

Dr Stanley Ng - Obstetrical and gynecological sonologist (Sydney) for providing fetal ultrasound images and movie clips.

4D Ultrasound

Fetal Face

(a) 24 weeks (b) 27.5 weeks (c - d) 32 weeks.	(a) 28 weeks neutral face (b) 33 weeks (c) 32.5 weeks (d) 33 weeks.

3D Ultrasound

3D Ultrasound Imaging

3D Ultrasound 12 week fetus

Three dimensional (3D) ultrasound scan images are generated from a series of images in 3 different planes. The image shows a 12 week fetal ultrasound images in the sagittal, axial and coronal planes that are used by the computer to generate the final 3D image in the lower right. Computers are able to generate these images in realtime, therefore in addition to static pictures, realtime 4D movies can be generated.

Cardiovascular

Cardiac
‎‎Heart TGA Page | Play	‎‎Hypoplastic Left Heart Syndrome Page | Play	‎‎Patent Ductus Venosus Page | Play

The heart is the first organ in the embryo that can be easily ultrasound visualised by its contractility. The absence of contractility also being a early diagnosis of embryo/fetal demise or trophoblastic disease.

The use of ultrasound at later stages of heart development in the mid-1980's began to be used as a diagnostic tool for congenital cardiac abnormalities.

Fetal ductus venosus ultrasound

Soft Markers

File:Ultrasound nuchal translucency

The term "soft markers" refers to ultrasound measurements which may not be diagnostic by themselves, but can have an indicative role for further diagnostic analysis of the pregnancy.

The Diagnostic Imaging Committee of the Society of Obstetricians and Gynaecologists of Canada in 2005 made the following recommendations:

1. The screening ultrasound at 16 to 20 weeks should evaluate 8 markers, 5 of which (thickened nuchal fold, echogenic bowel, mild ventriculomegaly, echogenic focus in the heart, and choroid plexus cyst) are associated with an increased risk of fetal aneuploidy, and in some cases with nonchromosomal problems, while 3 (single umbilical artery, enlarged cisterna magna, and pyelectasis) are only associated with an increased risk of nonchromosomal abnormalities when seen in isolation (II-2 B).
2. Identification of soft markers for fetal aneuploidy requires correlation with other risk factors, including history, maternal age, and maternal serum testing results (II-1 A).
3. Soft markers identify a significant increase in fetal risk for genetic disease. Timely referral for confirmation, counselling, and investigation is required to maximize management options (III-B).

Links: Ultrasound - Nuchal Translucency

Neural

Neural
‎‎Dandy-Walker Page | Play	‎‎Spina Bifida Page | Play

Anencephaly ultrasound

Ultrasound Placenta

Ultrasound can be used to measure both normal and abnormal placentation. Morbidly adherent placenta (MAP) is the general clinical term used to describe the different forms of abnormal placental implantation (Accreta, Increta and Percreta). Clinical ultrasound indicators of MAP are the presence of an interruption of the bladder line, absence of a retroplacental clear zone, and the presence of placental lacunae.

Placenta
‎‎Placenta Previa Page | Play	‎‎Vasa Previa Page | Play	‎‎Velamentous Cord Page | Play

Placenta Previa

Anterior placenta position (upper arrow) in relation to cervix os (lower arrow).	Posterior placenta position (arrow) in relation to cervix os (triangle).

Links: Placenta Abnormalities

Placental Cord

‎‎Velamentous Cord

Page | Play

Cord ultrasound

A number of clinical and diagnostic measurements can be made from ultrasound scans of the placental cord, including its insertion site with the placenta. Key measures are blood vessel number, measured by cross-sectional scan, and blood flow, measured by colour doppler.

• Cord
  • length (cm)
  • cross-sectional area (mm2)
  • coiling index
  • Wharton’s jelly area (mm2)
• Artery
  • cross-sectional area (mm2)
  • pulsatility index
• Vein
  • cross-sectional area (mm2)
  • absolute blood flow (ml/min)
  • blood flow for fetal weight (ml/kg/min)
  • blood flow mean velocity (cm/second)

Genital

Sex Determination

The earliest accurate ultrasound marker for fetal sex by ultrasound is at end of first trimester scan (12-13 weeks GA). Based upon direction of the genital tubercle when scanned in the sagittal plane ("sagittal sign").

• female - downward direction of the genital tubercle
• male - upward direction of the genital tubercle

Other sonographic landmarks can include:

• female - labial lines, uterus
• male - midline penis raphe, descended testis, micturition jet

Earlier embryonic sex determination can now be made by non-invasive genetic analysis techniques.

Links: Genital System Development | Non-Invasive Prenatal Testing

Twinning

Placental Membranes
Dichorionic diamniotic GA 13 week = 11 week	Monochorionic diamniotic GA 12 week = 10 week
Thick dividing membrane and "lambda" or twin peak sign at the junction with the placenta.	Thin dividing membrane and "T" sign at the junction with the placenta.
Links: Placenta Membranes

Dichorionic twins ultrasound

Transvaginal ultrasonography of dichorionic-diamniotic twins at 8 weeks and 5 days since co-incubation as part of IVF. The twin at left in the image is shown in the sagittal plane with the head pointing towards upper left. The twin at right in the image is shown in the coronal plane with the head pointing rightwards.

Ultrasound Research

Ultrasound imaging began in the 1950's but it was only with the application of computer analysis beginning in the 1980's that more detailed images could be generated. The increasing quality of ultrasonic equipment and computing allows today realtime 3D scans and calculations of fetal measurements as well as doppler measurement of heart rates.

In medical research there have been recent developments that allow spatial high resolution down to 30 microns in real-time.

Other Imaging Techniques

There are a range of other imaging techniques to study development and used in developmental research.

Other developmental research imaging techniques include:

• Magnetic Resonance Imaging
• Computed Tomography
• high frequency ultrasound or High Intensity Focused Ultrasound (HIFU)
• positron emission tomography (PET)
• single photon emission computed tomography
• optical bioluminescence
• fluorescence

Additional Images

• 

  Ultrasound uterine and ovarian vascularity

References

Journals

• Journal of Ultrasound in Medicine published by the American Institute of Ultrasound in Medicine.

Books

Molecular Imaging and Contrast Agent Database (MICAD) NBK5330 | PMID:20641179

Articles

Butt K & Lim K. (2014). Determination of gestational age by ultrasound. J Obstet Gynaecol Can , 36, 171-181. PMID: 24518917 DOI.

Lubusky M, Studnickova M, Skrivanek A, Vomackova K & Prochazka M. (2012). Ultrasound evaluation of fetal gender at 12-14 weeks. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub , 156, 324-9. PMID: 22660228 DOI.

Search PubMed

Search PubMed: Ultrasound prenatal diagnosis | Ultrasound

Prenatal Diagnosis Terms

• ART - Assisted Reproductive Technology a general term to describe all the clinical techniques used to aid fertility.

• blastomere biopsy - An ART preimplantation genetic diagnosis technique carried out at cleavage stage (day 3), excluding poor quality embryos, detects chromosomal abnormalities of both maternal and paternal origin. May not detect cellular mosaicism in the embryo.

• blastocyst biopsy - An ART preimplantation genetic diagnosis technique carried out at blastocyst stage (day 4-5), removes several trophoblast (trophoderm) cells, detects chromosomal abnormalities of both maternal and paternal origin and may detect cellular mosaicism.

• cell-free fetal deoxyribonucleic acid - (cfDNA) refers to fetal DNA circulating and isolated from the plasma portion of maternal blood. Can be performed from GA 10 weeks as a first-tier test or as a second-tier test, with women with increased probability on combined first trimester screening offered cfDNA or diagnostic testing.

• false negative rate - The proportion of pregnancies that will test negative given that the congenital anomaly is present.

• false positive rate - The proportion of pregnancies that will test positive given that the congenital anomaly is absent.

• free β human chorionic gonadotrophin - beta-hCG subunit of hCG used as a diagnostic marker for: early detection of pregnancy, Trisomy 21, spontaneous abortion, ectopic pregnancy, hydatidiform mole or choriocarcinoma.

• multiples of the median - (MoM) A multiple of the median is a measure of how far an individual test result deviates from the median and is used to report the results of medical screening tests, particularly where the results of the individual tests are highly variable.

• negative predictive value - The probability that a congenital anomaly is absent given that the prenatal screening test is negative.

• Non-Invasive Prenatal Testing - (NIPT) could refer to ultrasound or other imaging techniques, but more frequently used to describe analysis of cell-free fetal DNA circulating in maternal blood.

• polar body biopsy - (PB biopsy) An ART preimplantation genetic diagnosis technique that removes either the first or second polar body from the zygote. As these are generated by oocyte meiosis they detects chromosomal abnormalities only on the female genetics.

• positive predictive value - The probability that a congenital anomaly is present given that the prenatal screening test is positive.

• pre-implantation genetic diagnosis - (PGD, pre-implantation genetic screening) a diagnostic procedure for embryos produced through Assisted Reproductive Technology (ART, in vitro fertilisation, IVF) for genetic diseases that would generate developmental abnormalities or serious postnatal diseases.

• prenatal screening sensitivity - (detection rate) The probability of testing positive on a prenatal screening test if the congenital anomaly is present.

• prenatal screening specificity - The probability of testing negative on a prenatal screening test if the congenital anomaly is absent.

• quadruple test (maternal serum testing of a-fetoprotein Template:AFP, free B-hCG or total hCG, unconjugated estriol, and inhibin A) is a fetal chromosomal anomaly test usually carried out later in pregnancy (GA 14 to 20 weeks).

• single nucleotide polymorphisms - (SNPs) the variation in a single DNA nucleotide that occurs at a specific position in the genome.

• triple test - (maternal serum testing of a-fetoprotein Template:AFP, free B-hCG or total hCG, and unconjugated estriol) is a fetal chromosomal anomaly test usually carried out later in pregnancy (GA 14 to 20 weeks).

Terms

Ultrasound

• Biparietal diameter - (BPD) used to determine fetal age and normal development (small/large/abnormal) parameters. Measured as the diameter between the 2 sides of the head, measurements after 13 weeks (2.4 cm) to term (9.5 cm).

• cerebroplacental ratio - (CPR) a doppler ultrasound measurement calculated as the simple ratio between the middle cerebral artery pulsatility index (MCA‐PI) and the {{placenta]]l artery pulsatility index (UA‐PI). Fetuses with an abnormal ratio are thought to be a predictor of adverse pregnancy outcome such as: small for gestational age, abnormal fetal heart rate pattern, meconium stained liquor, low Apgar score, and acidosis at birth. PMID 28216258

• Crown-Rump Length - (CRL) measurement used in embryology to more accurately stage the early embryo and fetus. Measured from the curvature at the top (crown) to the curvature at the bottom (rump) of the "C-shaped" early embryo. Used in clinical ultrasound as a measurement between the periods of 7 to 13 weeks as an accurate estimation of the gestational age GA.

• DICOM - (ISO standard 12052:2006) Acronym for Digital Imaging and Communications in Medicine, a clinical standard for handling, storing, printing, and transmitting imaging information.

• Femur length - (FL) is used to determine fetal age and normal development (small/large/abnormal) parameters. The femur is the longest bone in the body and measurements and reflects the longitudinal growth of the fetus (approximately 14 weeks 1.5 cm - term 7.8 cm). It is one of the four typical ultrasound assessments of fetal size and age: Biparietal Diameter (BPD), |Head Circumference (HC), Abdominal Circumference (AC), and Femur Length (FL).

• Fetal size and age - typically measured using 4 ultrasound assessments: Biparietal Diameter (BPD), Head Circumference (HC), Abdominal Circumference (AC), and Femur Length (FL).

• Functional linear discriminant analysis - (FLDA) new growth assessment technique using serial measurements to discriminate between normal and abnormal fetal growth during 2nd and 3rd trimester.

• Head Circumference - (HC) Measured as an ellipse in a horizontal section at the level of the thalamus and the cavum septi pellucidi. 2nd trimester Fetal head growth

• Gestational sac - (GS) size formed initially by the chorionic cavity, after the embryonic period (week 8, GA W10) the amniotic cavity expands and fuses with the chorion. Measured by mean gestation sac diameter.

• inversion mode - an ultrasound processing method of volume analysis for the visualization of fluid-filled fetal structures such as; heart chambers, vessel lumen, stomach, gallbladder, renal pelvis, and the bladder. Post-processing inverts the gray scale of the volume voxels showing the normally anechoic structures in 3D or 4D renderings. This technique has been used to identify cardiac anomalies.

• Linear discriminant analysis - (LDA) to longitudinal data (James and Hastie, 2001)

• Mean gestation sac diameter - (MSD) = (length + height + width)/3. At week 3 (GAweek 5) MSD measures 2-3 mm. Normal MSD (in mm) + 30 = days of pregnancy.

• Mean yolk sac diameter - (MYD) can be used as marker for subsequent embryonic death or abnormalities (PMID 22215774).

• Spatiotemporal image correlation (STIC) - an image acquisition method used mainly for fetal heart analysis. Requires two steps; an automatic volume sweep, then image data analysis according to spatial and temporal domain generating an online dynamic 3D image sequence.

• Transabdominal scan - the ultrasound probe is placed on the external abdomen wall to scan pelvic region structures, conceptus and placenta. Also used to guide prenatal diagnostic techniques of chorionic villus sampling and amniocentesis.

• Transvaginal scan - (TVS) the ultrasound probe is placed inside the vagina and scans for female genital (uterus, ovary) and ectopic pregnancy.

• Termination of pregnancy - (TOP)

External Links

External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name. Links to any external commercial sites are provided for information purposes only and should never be considered an endorsement. UNSW Embryology is provided as an educational resource with no clinical information or commercial affiliation.

• Australian Society for Ultrasound Medicine - Guidelines For The Mid Trimester Obstetric Scan PDF (2005)
• American Registry for Diagnostic Medical Sonography - ARDMS Resources for Students and Educators

Glossary Links

Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link

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Cite this page: Hill, M.A. (2023, December 1) Embryology Ultrasound. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Ultrasound

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© Dr Mark Hill 2023, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G