- Early Pregnancy Ultrasound
- Nuchal Translucency scan
- Anomaly Scan
- Pregnancy Doppler Ultrasound
- 3D Pregnancy Ultrasound
- Chorionic Villous Sampling (CVS)
- Non-Invasive Genetic Test (NIPT)
Early Pregnancy Ultrasound
It is the first ultrasound examination that takes place between 6th and 7th week of pregnancy usually transvaginal. It is intended to locate the fetal sac that must be inside the uterine cavity. Depending on the examination week, the embryo can be seen and hear the heartbeat.
From the size of the sac or fetus, the gestational age can be calculated in women without a fixed cycle or an unknown last period.
Multiple pregnancy is recognized and chorionicity is confirmed, ie whether the embryos share a common placenta. Finally, there are problems such as fibroids or ovarian cysts.
Nuchal Translucency scan
Nuchal Translucency Ultrasound is performed from the beginning of the 11th to the end of the 13th week of pregnancy and is the first analytical examination of the fetus. This test, while initially aimed at checking for Down’s syndrome, has now been extended to include the assessment of the likelihood of another two trisomy but mainly the control of the basic anatomy of the fetus. Ultrasound findings are combined with the measurement of two hormones in the mother’s blood (PAPP-A, free β-hCG).
Nuchal Translucency is a liquid that is located in the fetal neck under its skin. All embryos have this fluid, but those suffering from Down syndrome have usually more fluid. In the 11-14 week ultrasound we also check the fetus for nasal bone, heart blood flow, as well as development and basic organs of the fetus.
With all the above measurements we can diagnose 9 out of 10 embryos suffering from Down syndrome (sensitivity of 92-95% for a false positive rate of about 3%). Similar are results for the calculation of risk of other serious chromosomal abnormalities, such as trisomy 18 and 13 and Turner syndrome.
What does the result of this examination mean?
The result you will eventually get will be a number that represents your personalized statistical probability of having a fetus with Down syndrome. This result is based on your background age, fetal measurements and the hormones in your blood. For example, if your result shows a probability of 1: 800, that means that if we had 800 women of the same age as you in the same weeks of pregnancy, one would be pregnant with a Down syndrome, while the remaining 799 would have normal embryos. Examination of 11-14 weeks can NOT assure you that the fetus does not have Down syndrome.
If the result indicates a probability greater than 1: 300, eg 1: 200 or 1:75, this means you should consult your doctor and decide together if you want to go to an invasive test like amniocentesis or CVS to check with certainty the embryo’s chromosomes.
The only way to be sure that the fetus does not have Down’s syndrome is to perform amniocentesis or CVS in which we examine genetic material from the amniotic fluid (amniocentesis) or placenta (CVS) that is identical to the genetic material (chromosomes) of the fetus.
The probability calculation for Down’s syndrome is world-wide controlled by the London Fetal Medicine Foundation (FMF, www.fetalmedicine.com) that developed this method. Its results have been confirmed in hundreds of thousands of women worldwide.
Doctors who perform the test are required to have the necessary proficiency certificates from the Fetal Medicine Foundation
Dr. Alexandra Georgakopoulou is internationally accredited by the FMF for the performance of all these special ultrasounds as well as by the Hellenic Ministry of Health – KESY.
What else does the ultrasound deliver at 11-14 weeks?
With this ultrasound, gestational age is accurately calculated, something particularly important for women with unstable cycles. Multiple pregnancies are evaluated for chorionicity, ie whether the embryos have separate placenta or common placenta, information which determines the progression of pregnancy and the way of monitoring. Finally, this ultrasound offers the possibility of a first gross estimation of the fetal anatomy so that a significant percentage of serious abnormalities can be detected at this early stage.
Anatomy (anomaly) Scan
Anatomy anomaly ultrasound scan is performed between 20-23 weeks and includes a series of measurements to control growth and to calculate the weight of the fetus, placental circulation, amniotic fluid assessment, and detailed check of fetal organs for congenital abnormalities .
The scalp, brain, face, spine, chest, heart, abdomen, kidneys, bladder, hands and feet are examined.
With this detailed ultrasound, about 70% of serious congenital abnormalities can be found.
Unfortunately, no ultrasound, however detailed and complete, can not rule out all the anomalies, nor guarantee the birth of a normal child.
The embryo is also tested for markers associated with chromosomal abnormalities. Approximately half of the Down Syndrome embryos have some marker, although most embryos with markers are normal. The results of the ultrasound at 11-14 weeks are taken into account in calculating the final probability for Down syndrome.
A Doppler colour ultrasound scan is also performed in the maternal uterine arteries. If increased resistance is found in the uterine arteries, this indicates an increased likelihood that the mother pre-eclampsia or the embryo develops low weight. In this case regular pregnancy blood pressure monitoring and monthly ultrasonography of the fetus are recommended.
Finally, the length of the uterine cervix is measured in order to evaluate the likelihood of premature birth. If the chance is found to be elevated then we will suggest appropriate treatment to reduce the likelihood of this serious complication.
Pregnancy Doppler Ultrasound
Doppler examines the blood flow to the fetal and placental vessels (usually the flow of the umbilical artery and the middle cerebral artery is checked). With this we receive information on the function of the placenta and the status of the fetus. This information is particularly important for small embryos and helps us decide whether a low-weight (small for the pregnancy week) embryo receives enough oxygen and nutrients from the placenta. Where flow to these vessels is not normal, more detailed and frequent testing is required.
3D Pregnancy Ultrasound
Three-dimensional ultrasound is performed between the 24th to 40th week of pregnancy.
With the help of the latest generation of ultrasound we can now have a three-dimensional image of the fetus, resulting from the synthesis of many two-dimensional images. We can also see 3D real-time embryo movements (4D)
Three-dimensional ultrasound can help us see some organs better, but it’s the two-dimensional ultrasound that will basically guide us to our diagnosis. The biggest advantage of 3D ultrasound is that it gives us the pleasure of seeing more “real” images of the fetus in its natural environment.
Chorionic Villous Sampling (CVS)
This invasive test is performed between 12-14 weeks of gestation.
This is a small operation that involves the ultrasonographic insertion of a thin needle in the uterus in order to receive a small portion of the trophoblast (the future placenta) which is sent for genetic examination. The placenta is derived from fertilized egg cells as well as the embryo resulting in the same genetic material as the embryo. By checking the genetic material in the trophoblast is like checking the embryo itself.
The material is tested in a molecular biology laboratory and the analysis (molecular karyotype) includes all the 23 pairs of chromosomes as well approximately 500 genetic syndromes that are associated with mental retardation. The process lasts few minutes and as with all invasive methods there is a small risk of excretion of about 0.5-1%.
This examination takes place after the 16th week of pregnancy.
This is an easiest operation compared to CVS and does not require anesthesia. It involves the ultrasound entry of a thin needle into the uterus in order to aspirate the amniotic fluid for examination. The amniotic fluid contains cells from the embryo, so controlling the genetic material in the liquid is like controlling the embryo itself.
The material is tested in a molecular biology laboratory and all 23 chromosome pairs are analyzed as well as about 500 syndromes related to mental retardation (molecular karyotype)
The process lasts for a few minutes and as with all invasive methods there is a small risk of excretion of about 0.5-1%
Non-Invasive Genetic Test (NIPT)
From very early in pregnancy, small cells of placental cells are released in the maternal circulation. The placental cell DNA is the same as that of the fetus. With modern and complex techniques, it was possible to isolate this fetal DNA and, with specialized analyzes, we can detect Down syndrome embryos with an accuracy of about 99%. Confirmation with amniocentesis is of course necessary, but the detection rate is extremely good for screening. Very high (> 95%) are detection rates for trisomies 13 and 18, while a little lower for chromosomal abnormalities related to sex chromosomes.
Since the number of abnormalities that can be detected is limited, the method is not recommended in cases where ultrasound findings are found, including increased neck translucency. In such cases an invasive control (amniocentesis or CVS) should be performed.
Detection techniques are evolving, and some rare genital syndromes such as Di George et al. Can still be controlled, and there is still considerable controversy over the suitability of the method, mainly because of the many false positive results. The test is also suitable for twin pregnancies and pregnancies after IVF
For the non-invasive test to be reliable, the fetal fraction of free DNA must be at least 4%.