The ultrasound was first routinely used in medicine over 40 years ago and it became a very useful diagnostic tool in the fields of gynaecology and obstetrics. It is included in non-invasive methods and unlike other radiological methods, there is no ionizing radiation and thermal and cavitation mechanisms with the proper settings of ultrasound apparatus are negligible.
World Federation for Ultrasound in Medicine and Biology has confirmed that in diagnostic use- grayscale there is no risk of harmful consequences during an embryogenic period (first trimester). This means that ultrasound is a safe way of monitoring your fetus during the pregnancy. In Polyclinic Arcadia we use ultrasound equipment of the newest technology which enables 2D and 3D pictures to be displayed. For this purpose, sound waves of frequencies between 3,5 and 7,0 are mainly used. Why and when is ultrasound used during pregnancy?
In a group of routine ultrasound examinations is included examination around 7th week with a transvaginal probe to confirm intrauterine pregnancy, confirmation of cardiac activity and frequency of fetal heart, confirmation of possible multiple pregnancies and number of placentas, exclusion of pathological forms of pregnancies, measurements of the size of fetus in order to determine the due date and exclusion of cystic forms on an ovary and uterine malformation.
The second ultrasound examination should be planned around 11-13+6 weeks of pregnancy – the best is 12th week- with a transvaginal probe due to Mini anomaly scan (see below).
The third ultrasound is performed through transabdominal probe between 18th and 22nd week – Anomaly scan- genetic screening (see below) + transvaginal probe measurement of cervix length. (see below).
Further ultrasound examinations are performed in 28th, 31st, 34th and 36th week due to evaluation of foetal growth, the amniotic fluid quantity, placenta position, foetal position and doppler monitoring of foetal and placenta flows. After 38 weeks, we recommend ultrasound monitoring of pregnancy in a selected maternity ward. The reasons for ultrasound examination, outside the routine examination, are: doubt in the calculation of the due date, vaginal bleeding, pelvic pain, suspicion of cervical insufficiency, amniocentesis, differences in the clinical size of the uterus and calculated gestation, multiple pregnancies, suspicion of amniotic fluid leakage, evaluation prior to determined suspected anomalies, abnormalities in fetal growth and amniotic fluid quantity, suspicion of intrauterine death of the fetus, pelvic tumour formations, uterine malformations etc.
In Polyclinic Arcadia, following ultrasound examination models during pregnancy re possible:
The doppler has been used for a long period to detect fetal pulse. Recent development in technology during the last several years has enabled extensive distribution and use in obstetrics, particularly in the field of evaluation and monitoring of the fetal condition, its progress in terms of intrauterine growth restrictions and diagnosis of cardiac malformations. Doppler ultrasound today is the most widely used in detecting fetal heart rates and pulsing in different fetal blood vessels. Blood vessels which are usually examined are: umbilical artery, aorta, central cerebral artery, uterine arcuate artery and inferior vena cava. With color-doppler use, you can clearly see blood flow in the veins of the fetus in a time period and as well as direction of motion, and everything is represented in different colours. Color-doppler is especially important in the diagnosis of fetal heart defects and flaws of the blood vessels and in assessing haemodynamic reactions to fetal hypoxia and anaemia.
Two-dimensional ultrasound has represented a gold standard of sonography for more than 40 years. With 3D ultrasound development, we’ve gotten the ability to scan the entire volume of ultrasound information of a particular anatomical area. The computer processes these images and presents them as a three-dimensional image. By doing so, the ultrasonic operator can obtain anatomical sections that could not be available using an ordinary 2D ultrasound machine. There are several types of displays in 3D technology. For anatomy analysis it is the most important is MPRI – multiplanar reconstruction of the third C plane and for the patient the most interesting is surface-rendering model of depicting which can for example show the face of fetus in the uterus.
4D picture quality (possible artefacts) still depends on doctor’s skills, then on the quantity of amniotic fluid which surrounds the foetus, position of the foetus, movements of the foetus, acoustic shadows and possible pregnant woman’s obesity. 4D/3D ultrasound during pregnancy can help in discovering malformations of foetal face (cleft lip, or palate, micrognathia), malformation of extremities, neural tube defects (spina bifida), some of malformations of the brain- visualisation corpus callosum. In gynaecology we use it for diagnostics of uterus malformations and to diagnose positions of polyp, myoma and intrauterine spirals.
MINY ANOMALY SCAN
It indicates ultrasound screening for fetal chromosomal defects and a part of structural anomalies already in the first trimester of the pregnancy. Chromosomal screening should be done in the 11-13+6 week of the pregnancy, but since with 12 weeks there is a visible part of structural anomalies, in Polyclinic Arcadia we recommend examination when the pregnancy reaches 12 weeks.
- Fetal nuchal translucency (NT or NN)- space measuring of fetal nuchal translucency – that space with fetus which has a Down syndrome, T-21, significantly rises. The strongest is an independent ultrasound screening marker for Down syndrome (77% detection rate) and it also point to possible cardiac anomalies, TORCH infections + parvovirus and lymphatic system anomalies.
- Combined test NT+ serum markers (PAPP-A and f-bHCG) in 12th week (85% detection rate- in comparison with Triple test and mother’s age which is 50-70%). At risks 1:50-1:100 and more, invasive prenatal diagnostics CVS is indicated. At risks 1:100-1:1000 recommendation is to do other early ultrasound markers, to repeat ultrasound in the 14th week due to evaluation regression NT, triple test in 16th week, Genetic-screening ba anomaly in 19th week and opt for early amniocentesis and at very low risks, less than 1:1000, usual routine examinations.
- Presentation of the septicaemia cystic hygroma, foetal m. bladder, exomphalos
- Nasal bone+
- Color doppler Ductus venosus +
- Tricuspid regurgitation +
- Frequency of fetal heart+
- Color doppler IVC
- Color doppler a. uterine – with exclusion of notching in 12-13+6 week, possibly in combination with PAPP-A indicates a lower risk of some of the more common complications during pregnancy preeclampsia- high blood pressure, stagnation in the growth of foetus and placental abruption in pregnancy.
- The anatomy of the foetal brain, extremities, view of stomach and fetal dynamics.
ANOMALY SCAN (GENETIC SONOGRAM) IN II TRIMESTER
Minimum of 10-15% of all conceived pregnancies are chromosomally abnormal. Such pregnancies are the most frequent cause of miscarriages and one of the common causes of structural anomalies, intrauterine fetal death and mental retardations. The most common autosomal trisomy in live births is trisomy 21. The risk significantly grows with the age of a pregnant woman. The frequency of chromosomal abnormalities: Down syndrome 1/800 childbirths, trisomy 18 Edwards syndrome 1/8000 childbirths and trisomy 13 Patau syndrome 1/5000-20000. Specific risk for trisomy 21 during amniocentesis for a 35-year-old pregnant woman is 1/274 and for a 48-year-old pregnant woman 1/10. General risk for a repetition of pregnancy with chromosomal abnormalities is 1%. In 1970, first screening was introduced and amniocentesis was done to all pregnant women above the age of 35. Since the risk od miscarriage directly related to the procedure is 1/270, serum screening is introduced. Triple test is used in diagnostics- serum screening test for chromosomal abnormalities T21 and T18- 15-20 weeks, but the most accurate is from 16-18 weeks (aFP, unconjugated estriol, hCG). Only 60-65% of all pregnancies is identified with chromosomal abnormality T21. Until recently it was a routine practice to send a pregnant woman (pregnant woman older than 35, chromosomal abnormalities in the family, abnormal results in Triple test) to an invasive examination of amniocentesis.
Using only age as a criterion, 140 amniocenteses should be done to find one foetus with Down syndrome which means that one healthy foetus has to be lost to detect two foetuses with Down syndrome. When we use combined criterion of pregnant woman’s age with Triple or Double test, then 60 amniocenteses should be done and one healthy foetus is lost to detect three or four foetuses with Down syndrome. However, during past ten years, it is determined that chromosomal abnormalities are related to large or small structural anomalies of the foetus and with ultrasound markers, which we can recognize during the ultrasound examination of a pregnant woman in the II trimester. Due to that, a quality ultrasound examination in the I and II trimester, should reduce the number of unnecessary invasive diagnostic procedures such as early amniocentesis and CVS.
Foetuses with 18 and 13 trisomy have a lot of large structural anomalies which are relatively easy to identify on the ultrasound examination (over 90%) and at least 4 smaller structural anomalies (markers), but it can not be applied with Trisomy 21 (Down syndrome) where large structural anomalies are visible in the 19th week of pregnancy with only 25% of pregnant women. That’s why the practice is introduced with a genetic sonogram which requires sonographic soft markers that select high-risk pregnant women, who are then with the Triple test results directed to invasive method of diagnostics- amniocentesis. Such markers are anatomical variations of the foetus which besides being related to a greater risk of aneuploidy, do not have clinical significance. They usually disappear during foetal development and it is also possible to find named abnormalities with the foetuses of a normal karyotype. The risk rises with a low-risk pregnant woman (age under 35, triple test 1:275- 1:1000- medium and 1:1000 and less- low) if more markers are detected in or one isolated strong marker -NN, nasal bone or a larger structural anomaly with a high-risk pregnant woman and with one isolated ultrasound marker.
Two thirds of foetuses with Trisomy 21- Down syndrome have 2 or more positive ultrasound markers.
From major structural anomalies, it is possible to diagnose a part of congenital heart defects (VSD- ventricular septum defect, atrioventricular canal) duodenal atresia- 30% risk for Down syndrome, cystic hygroma especially septicaemia cervical form-72%, non-immune generalised hydrops-16%, isolated hydrothorax 5%, diaphragmatic hernia 10-20%, omphalocele 30-40% and exceptionally 87% it the liver is properly positioned inside the abdomen, extended lateral brain chambers – ventriculomegaly (isolated mild 10-15 mm, often with foetuses of a normal karyotype), hydrocephalus, spina bifida isolated up to 33%, Dandy-Walker malformation, cerebral hypoplasia with the increase of cyst magna, agenesis corpus callosum- requires 3D scan, holoprosencephaly, micronation, cleft palate- requires 3D scan, cleft lip isolated low risk, hypertelorism and hypertelorism, urethro-vesical obstruction, multi-cystic dysplastic kidney…
From soft sonographic markers (isolated are not an indication for amniocentesis) we follow nuchal translucency (the most important marker 43%- and as independent sign in the II trimester, although it later comes to disappearance of callus) length of long foetal bones- femur, humerus, pielectasia- widening of a kidney canal for more than 4 mm, echogenic intracardiac foci of brightness of bone type (especially the right ventricle or both), hyperechoic intestinal type of bone brightness, the cyst of coronal plexus bilaterally, multiple, are above 10 mm big, nasal bone absence or hypoplasia (strong marker 40%), expansion of iliac wings bones- dysplasia of foetal pelvis above 90°, ear length, less than 10 percentiles, feet deformities club foot, rocker bottom foot, clinodactyly- medium phalanx hypoplasia of the fifth finger on the hand- relation towards the fourth finger, sandal gap- separation between 1st and 2nd toe, mutually fixed hands with clenched fists, polydactyly, one umbilical artery..
ULTRASOUND OF MEASURING CERVICAL LENGTH
CL cervical length – length of cervix is a factor that predicts forward or premature birth. Normal value of CL usually results with birth close or around the due date. It is very important in a twin pregnancy, without the preventive operative procedure of cerclage, especially in the case of monochorionic twins (one placenta).
15th-24th week of pregnancy, CL shorter than 20-25mm, risk for premature childbirth before the 32nd week rises to 50%
25-28 weeks of pregnancy CL shorter than 20-25 mm, risk is from 20-28% and above 35mm, very low risk for the childbirth before the 34th week of pregnancy.
If the ultrasound examination verifies shortened cervix in the period of 15 to 24 weeks, then, especially in twin pregnancies, preventive surgical procedure of cerclage is being indicated.
ULTRASOUND MONITORING OF MULTIPLE PREGNANCIES
Ultrasound has caused a revolution in antenatal care of multiple pregnancies. Before of the introduction of ultrasound, 50% of twins were discovered only during childbirth. The rate of mono-ovum (mono-zygotic) pregnancies is 1/250 pregnancies (it is formed by a merger of one sperm and one oocytes). Double-oved rate (dizygotic) depends on the race, geography region, mother’s age, availability of assisted reproduction methods. It varies from 1.3/1000 of live births up to 49/1000 live births. (it is formed by merging 2 sperms and 2 oocytes) Extremely important factors which can be determined only by the ultrasound, help in predicting and diagnosing complications of multiple pregnancies (chorionicity- number of placentas, cervix length, structural anomalies, chromosomal abnormalities, complications characteristic only for multiple pregnancies- TTTS, mono-chorials, monoamniariums, stuck twin, vanishing twin, acardiac twin).
If we name only some of the risks, it is clear what is the purpose of ultrasound in monitoring multiple pregnancies. 14-25% in growth retardation of the foetus, 4 times higher risk for cerebral paralysis with twins and 17 times higher risk with triple-foetus pregnancies, 4 times higher risk foetal death during pregnancy, 2 times higher risk for structural anomalies in twin pregnancy (in one-gender pregnancy is 2-3%), risk for chromosomal abnormalities of foetus is increased is like for older pregnant woman, 3-4 years.
Discordant growth of twins results in different foetal weight. The foetus with a growth restriction has a much higher risk for adverse outcome. Only with a serial ultrasound measuring it is possible to determine the difference in growth. The early difference, usually since the 16th week, -cause TTTS- connected blood circulation of twins in one placenta with an unbalanced direction of blood, or already since 11th to 14th week the difference greater than 10%, risk for structural and chromosomal anomalies is 10 times higher.
Later difference after 30th to 32nd week- placenta usually becomes functionally insufficient for a proper growth in comparison to singleton pregnancy. In all ultrasound examinations in our Polyclinic, color doppler is used and its contribution in early predicting of complications through measuring flows of placental, foetal and uterine blood circulation.
Number of ultrasound examinations and weeks of pregnancy during which ultrasound examination of multiple pregnancy should be performed.
In the first trimester, 2 examinations are required. In 7th and 9th week in order to diagnose a future number of placentas (chorionicity- number of chorionic bags, number of yolk bags, number of amniotic bags, characteristics of a membrane division, a membrane thickness, frequency of foetal heart) and in that way give advice about possible risks to future parents.
12th week of pregnancy mini anomaly scan+ combined test (+triple test recommendation in the 16th week with twins due to a lower sensitivity of the test).
Later, the usual period between the ultrasound examinations in multiple pregnancies is once a month, but with the suspicion of growth difference, time interval is 2 weeks. With mono-ovum twins, it should be done in the interval between 16th and 22nd week, due to the TTTS risk the interval is 2 weeks as well.