prenatal diagnosis within the Obstetrics, detects problems or anomalies that affect the health of the fetus during pregnancy. Defects or anomalies called congenital that appear in the fetus when it is inside the uterus, can be seen in pregnancy through prenatal diagnostic tests of our medical services.
Some examples of congenital defects are Down syndrome, babies who have spina bifida (a birth defect that affects the spine), and also babies with heart disease, etc.
If there is a hereditary disease in the family, the doctor can also study through prenatal diagnosis if the baby is at risk.
El Institute of Obstetrics and Gynecology in Barcelona, by Dr. Gómez Roig has specialists in prenatal diagnosis that will accompany you during the pregnancy to offer you the best possible care.
If a baby has problems already inside the womb. We study it and advise the mother and her family with the maximum information available.
How is prenatal diagnosis performed?
El prenatal diagnosis Its purpose is to diagnose a possible congenital defect or existing anomaly already in the prenatal phase.
We currently have different tools to perform prenatal diagnosis. The available techniques can be classified into:
- Non-invasive prenatal diagnostic techniques (first trimester screening and free fetal DNA in maternal blood)
- Invasive prenatal diagnostic techniques (amniocentesis and chorionic biopsy).
Since invasive prenatal diagnostic techniques carry a risk, it is not possible to universalize their use. Therefore, it is necessary to establish criteria to select a risk population using non-invasive techniques. A first trimester screening is the initial non-invasive test that is performed on all pregnant women during pregnancy.
El first trimester screening It is a study that is based on a maternal blood test and an ultrasound between 11 and 13 weeks of pregnancy. The results of the two tests mother's blood test and first trimester ultrasound They give a numerical value that defines the risk.
This screening should be offered to all pregnant women regardless of their age. In the first trimester ultrasound, a marker is studied that is used to calculate the risk called "nuchal fold".
La ultrasound done in second trimester (19-21 weeks of pregnancy), performs a study of the fetal anatomy, and also reinforces prenatal diagnosis by studying the existence or not of structural pathologies (fetal malformations).
invasive techniques The most widely used, recommended in the population at risk detected by the first trimester screening, are the amniocentesis and chorionic biopsy.
These techniques should be offered to obtain material from the fetus in order to carry out a chromosomal or gene study. Chromosomes are cell structures that contain thousands of genes.
What is the non-invasive prenatal test?
El non-invasive prenatal test It is one that does not present risks for the mother and the baby and includes:
- First trimester screening (mother's blood test and first trimester ultrasound).
- Study of abnormal Fetal DNA in maternal blood.
The first trimester screening is included in the usual pregnancy control. The detection of fetal DNA is not currently contemplated in the mutual or social security coverage.
In the imminent future, it is expected that fetal DNA will be included in the portfolio of services in a specific population of pregnant women.
What is the study of fetal DNA?
The fetal DNA study in maternal blood has been one of the most promising discoveries in the field of prenatal diagnosis.
These non-invasive techniques to detect chromosomal abnormalities using the Fetal DNA free in maternal blood provide a number of important advantages for detecting fetal abnormalities.
Chromosome alterations regarding invasive techniques amniocentesis or chorionic biopsy.
Non-invasive tests do not present the risk of fetal loss, nor the physical and psychological discomfort that invasive techniques present.
One of the clearest indications for performing a fetal DNA study on a maternal blood test is in those pregnant women who present a high and intermediate risk in the first trimester screening.
Several studies have shown good sensitivity and specificity of this non-invasive test for different chromosomal abnormalities.
The fetal DNA study in maternal blood is a good choice to better classify the risk, but at the same time we must know that it is not a definitive diagnostic technique.
If the result of the study is high risk, it should always be complemented with an invasive technique (chorionic biopsy or amniocentesis depending on the weeks of pregnancy) to establish a definitive diagnosis. If the test is low risk, then we can be calm.
It is only in cases of high risk of fetal involvement when the study should be completed.
Amniocentesis
La amniocentesis It is an invasive technique that allows obtaining a little amniotic fluid by introducing a needle through the maternal abdominal wall.
In addition, amniocentesis can be performed from 15 weeks of gestation, although it is advisable to perform it from 16 weeks.
This test is usually done to find out if the fetus has a problem with the genes or chromosomes. As the Síndrome de Down.
This might be done if another test, such as first-trimester screening, shows that the fetus might be at risk for a chromosome problem.
How is an amniocentesis performed?
Amniocentesis is performed as follows:
- The doctor does an ultrasound to see the fetus and the amniotic fluid around it.
- If the same doctor watches the ultrasound screen while inserting a needle connected to a syringe into the pregnant woman's abdomen to obtain some amniotic fluid.
- The amniotic fluid is sent to a laboratory for study.
Does amniocentesis have any risks?
Amniocentesis may have some risk. Complications are very rare, but they can also exist. The risks of amniocentesis may include the following:
- Loss of amniotic fluid.
- Infection.
- The needle can touch the baby, which in rare cases can cause injury.
- Blood from the placenta can contaminate maternal blood. This can cause problems in subsequent pregnancies if there is Rh incompatibility. It is for this reason that Rh-negative pregnant women are given a vaccine after the test.
It is known that currently the risk of miscarriage after amniocentesis is 0,1-0,2%.
Should I worry about anything after amniocentesis?
You should be concerned after amniocentesis depending on the clinic you have and the severity of it. After amniocentesis, it is normal to feel mild cramps in the belly for a short period of time. On the other hand, you should call your doctor if:
- Bleeding or fluid leaking from the vagina.
- You have increasingly severe belly cramps.
- If you have a fever above 38ºC.
Chorion Biopsy
chorion biopsy it is an invasive test. In chorionic villus biopsy, a small piece of the placenta is removed, which is the organ found inside the uterus of a pregnant woman. It supplies the fetus with nutrients and oxygen, and removes waste. The fetus and the placenta have many genes in common.
In the chorion biopsy, it can be detected if there is a problem with the genes or chromosomes of the fetus.
When is the chorion biopsy done?
chorion biopsy it can be performed between 10 and 14,6 weeks, although it is preferable between 11 and 13,6 weeks of pregnancy. This biopsy can be done before amniocentesis. If the risk of fetal involvement is suspected early, the technique that can be performed as soon as possible is chosen. For this reason, chorionic biopsy is sometimes preferable to amniocentesis if the information is to be available more quickly.
How are chorionic villus biopsies performed?
In carrying out the chorionic biopsy, the choice of the way to obtain the small tissue of the placenta will depend on the weeks of gestation, the placental location and the experience of the person who performs it. The biopsy can be through the abdomen like amniocentesis or vaginally.
This chorionic biopsy is performed as follows:
- The doctor performs an ultrasound to visualize the uterus, fetus, and placenta.
- While looking at the image, the doctor places a small needle in the abdomen or a small clamp in the vagina.
- It then inserts the needle or forceps into the placenta and takes a very small sample of tissue.
- The tissue is sent to a laboratory for study.
Does chorionic biopsy have any risks?
chorionic biopsy has some risk. Among the existing risks, the risk of miscarriage is similar to that of amniocentesis, around 0,2%, when performed by an experienced person. Complications are rare, but there can be.
The risks of chorionic biopsy may be the following:
- Spontaneous abortion.
- Blood from the placenta can contaminate maternal blood. This can cause problems in subsequent pregnancies if there is Rh incompatibility. It is for this reason that Rh-negative pregnant women are given a vaccine after the test.
Should I worry about anything after a chorionic biopsy?
You should worry, after a chorionic biopsy, depending on the symptoms you have and how severe they are. After a CVS, it is normal to have some bleeding from the vagina.
If you are concerned you should call your doctor. You must also notify whenever you present:
- Vaginal bleeding that resembles that of a menstrual period.
- Leakage of fluid from the vagina.
- You have increasingly severe cramps.
- If you present, you have a fever above 38ºC.
El Institute of obstetrics and gynecology of Dr. Gómez Roig, in Barcelona, has specialists in prenatal diagnosis that will accompany you during the pregnancy to offer you the best possible care.
Prenatal Diagnosis Video
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High Resolution Ultrasound
3D and 4D ultrasound
- About the Author
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Head of the Obstetrics and Gynecology Service at the Sant Joan de Déu Hospital in Barcelona. Associate Professor of Obstetrics and Gynecology and Coordinator of the Sixth Course of Medicine at the University of Barcelona, UB. Director of the Dra. Gómez Roig Institute and Coordinator of Obstetric and Gynecological Processes at the Corachan Clinic in Barcelona.