Diagnostic Tests of Prenatal Testing
—- AMNIOCENTESIS —-
This serious service is done after the 16th week of pregnancy until the time of delivery
With amniocentesis, we detect and diagnose the quality of the embryo during its endometrial life, whether is normal or suffers from any chromosomal defect such as Down’s syndrome, Patau and Edwards (trisomies 21, 13 and 18 respectively). We also detect gene diseases such as sickle cell anaemia, cystic fibrosis etc.
Amniocentesis is an incisive method, which is performed by inserting a thin needle without anaesthesia in the uterus under continuous checking of ultrasound in order to gain small quantity of amniotic fluid, which surrounds the embryo. The duration of the procedure is one minute.
The cells inside the amniotic liquid come from the baby. The amniotic fluid removed from amniocentesis will be recovered in some hours from the baby’s urine. Amniocentesis is an incisive method and has dangers for abortion in only 1% rate. It abortion happens; it will be done during the next five days after the amniocentesis. Frankly, the danger of hurting the embryo is limited very low for both the baby and the mother.
After the above procedure, the amnionic liquid is going in a genetic lab and the results include the most frequent anomalies (Down’s syndrome, Patau and Edwards, and the sex of the baby), which are obtained in 24 to 48 hours with rapid analysis QF-PCR and credibility of 98%. This test is completed within 2 weeks with the final result, which is called the karyotype of the embryo.
—- NUCHAL TRANSLUCENCY SCREENING (NT) —-
The Nuchar translucency screening is a test, which is performed within the 11th-13 weeks 6 days in order to check which embryos have the possibility or the risk factor to suffer from genetic syndrome (Down, Patau and Edwards or trisomies 21, 13 and 18 respcetively.
The Nuchar translucency of embryos is a collection of liquid which is located in all embryos behind the neck of the spinal cord and specifically between skin and muscles of embryos.
The Increased fetal NT thickness is investigated by the measurement of NT and raises the possibility of embryo risk to suffer from Down, Patau and Edwards syndromes, which dos not always mean that the embryo will have anomalies.
It has to be stressed that the investigation of chromosomal anomalies is performed with the ultrasound screening within 11-14 weeks in relation with level 2 ultrasound scan (has low sensitivity in the detection of chromosomal anomalies about 40% for detection of Down’s syndrome).
The test is performed with the protocol from Fetal Medicine Foundation-FMF). For the risk 4 ultrasound scan factors are calculated, which the following:
- to measure the collection of fluid behind the fetal neck (nuchal translucency)
- to examine the fetal nose and palate
- to measure the fetal heart rate
- to assess the flow of blood across the tricuspid valve of the fetal heart and the ductus venosus
- Fetal anatomy
- Maternal age
- A maternal blood sample for the measurement of the placental products of free ß-hCG and PAPP-A
- Family medical background and the mother’s previous pregnancies
The final individualized specific risk factor is given by an approved software for Greece called Astraia and ONLY if ALL above markers combine, then the defected embryos can be detected with high accouracy which approaches 97% (for Down’s syndrome). The non usage of one of the above parameters decreases the sensitivity to the test.
Also it can be tested:
- The length of the cervix of the uterus for the possibility of the premature birth
- The Doppler flow jn uterine artery for the estimation of the possibility of preeclampsia and the IUGR.
Time of the examination approximately 40 minutes
—- CHORIONIC VILLUS SAMPLING (CVS) —-
Chorionic villus sampling (CVS) is a test done during early pregnancy that can find certain problems with your baby (fetus). It is generally done when either you or the father has a disease that runs in the family (genetic disorder). It may also be done when you are over age 35—being over 35 increases your chance of having a baby with a chromosome defect.
Chorionic villi are tiny finger-shaped growths found in the placenta. The genetic material in chorionic villus cells is the same as that in the baby’s cells. During CVS, a sample of the chorionic villus cells is taken for biopsy. The chorionic villus cells are checked for problems. The procedure is generally done late in the first trimester, most often between the 11th and 14th weeks.
The chorionic villus sample can be collected by putting a thin flexible tube (catheter) through the vagina and cervix into the placenta. The sample can also be collected through a long, thin needle put through the belly into the placenta. Ultrasound ιs used to guide the catheter or needle into the correct spot for collecting the sample.
If you have a family history of certain diseases, CVS can be used to find genetic disorders, such as Tay-Sachs disease or hemophilia. It can also find chromosomal birth defects, such as Down syndrome. CVS cannot find neural tube defects, and it cannot be used to see if the baby’s lungs are mature.
Chorionic villus sampling can be done earlier in pregnancy (at 11 to 14 weeks) than amniocentesis (usually done at 15 to 20 weeks). This allows you to know the health of your baby and make an earlier decision whether to continue or end the pregnancy. Results of CVS can be available sooner than amniocentesis results.
You might consider chorionic villus sampling if:
- You had positive results from a prenatal screening test. If the results of a screening test — such as the first trimester screen or noninvasive prenatal testing — are positive or worrisome, you might opt for chorionic villus sampling to confirm or rule out a diagnosis.
- You had a chromosomal condition in a previous pregnancy. If a previous pregnancy was affected by Down syndrome or another chromosomal condition, this pregnancy is at higher risk, too.
- You’re 35 or older. Babies born to women 35 and older have a higher risk of chromosomal conditions, such as Down syndrome.
- You have a family history of a specific genetic condition, or you or your partner is a known carrier of a genetic condition. In addition to identifying Down syndrome, chorionic villus sampling can be used to diagnose many other genetic conditions — such as Tay-Sachs and cystic fibrosis.
Rarely, your health care provider might caution against transabdominal chorionic villus sampling — which is done through the abdominal wall — if:
- Your uterus is severely titled backward and you have intestinal loops between your abdominal wall and uterus
- Your placenta is located at the back of your uterus and your baby is blocking access to it
Rhesus (Rh) factor — an inherited trait that refers to a specific protein found on the surface of red blood cells — matters, too.
Your health care provider might caution against both types of chorionic villus sampling if you’re Rh negative, your baby’s father is Rh positive and you’re sensitized — your body has already begun to produce antibodies after exposure to the baby’s red blood cells at some point during pregnancy. If you’re sensitized and have chorionic villus sampling, you’re at increased risk of complications following chorionic villus sampling.
—- LEVEL 2 ULTRASOUND — AN ULTRASOUND ANATOMY SCAN —-
A level 2 ultrasound scan refers to a special type of scan to assess the fetus for structural abnormalities. A qualified and experienced doctor, who has acquired the skill to do so does this. It is usually carried out between 18-22 weeks of pregnancy in order to detect fetal abnormalities that may compromise the quality of life, and gives the parents options for treatment or termination of the pregnancy
The ultrasound anatomy scan, or level 2 ultrasound, is an amazingly interesting experience for parents-to-be. Your baby will be measured from crown to rump (and what a cute rump it is!), around her middle, around her head — and that’s just for starters. The four chambers of the heart will be viewed, as well as the kidneys, bladder, stomach, brain, spine, and sex organs. A level 2 ultrasound can also tell you the sex of your baby if you haven’t already found out through noninvasive prenatal testing (NIPT). Remember: Be sure to tell your sonographer if you don’t want to know!
Measurements are taken from this special ultrasound during pregnancy to make sure your baby is growing appropriately (and that his or her gestational age is still on target). A survey of the organs, including the umbilical cord, ensures that they are developing normally (or identifies any potential problems as soon as possible). The sonographer will also be looking at your amniotic fluid levels, the location of the placenta, and the fetal heart rate. Settle in to enjoy the show: The detailed level 2 scan can take 30 to 45 minutes (depending on how cooperative your little one wants to be during the photo shoot).
Who a level 2 ultrasound is for
Most practitioners order an ultrasound anatomy scan for all their moms-to-be.
How a level 2 ultrasound is done
You recline on an exam table with your belly exposed. A sonographer applies gel and then moves the transducer over your abdomen. As sound waves emitted from the transducer bounce off “structures” inside (like your baby’s adorable face!), images are formed on a video screen. To get the most comprehensive assessment, the sonographer will be aiming for many different views from lots of different angles in this anatomy scan. When the technician gets a clear shot, he or she will freeze-frame the picture (that’s the actual sonogram) and then measure the anatomy. You can expect to go home with one or two good sonogram pictures (the perinatologist and your practitioner will review the rest).
When a level 2 ultrasound is done
Most anatomy scans are performed in the second trimester of pregnancy between 18 weeks and 22 weeks. If you have a condition that needs to be monitored (such as carrying multiples), you may have more than one detailed ultrasound.
Duration of the test 40-60 minutes
Risks: There are no significant risks associated with ultrasounds, though medical guidelines caution against unnecessary exposure to ultrasound — which is why your practitioner will schedule only a handful of them throughout your pregnancy.