First trimester screening

Nicole Wendler holds a PhD in biology in the field of oncology and immunology. As a medical editor, author and proofreader, she works for various publishers, for whom she presents complex and extensive medical issues in a simple, concise and logical manner.

More about the experts All content is checked by medical journalists.

The first trimester screening is a voluntary examination in early pregnancy. Doctors use maternal blood values, ultrasound measurements on the unborn child and various risk factors to calculate the risk of chromosomal changes or malformations in children. Read here what the first trimester screening examines in detail, what consequences a positive result can have and what you should consider.

What is first trimester screening?

The first trimester screening is also called first trimester screening or first trimester test. It is a prenatal examination in the first trimester of pregnancy for genetic disorders in the child. However, the screening only allows the calculation of the probability of genetic diseases, malformations or chromosome changes; This cannot be used to prove this directly.

What is examined in the first trimester screening?

During the first trimester screening, the doctor takes blood from the expectant mother and performs a high-resolution ultrasound examination on the unborn child:

Determination of blood values in maternal serum (double test):

PAPP-A: Pregnancy Associated Plasma Protein A (product of the placenta)
ß-hCG: human chorionic gonadotropin (pregnancy hormone)

High-resolution ultrasound examination of the child:

fetal neck transparency (see below)
Length of the child's nasal bone
Blood flow through the right valve of the heart
venous blood circulation

A very important part of the first trimester screening is the measurement of the fetal neck transparency (neck fold measurement, NT test). In every child between the 10th and 14th week of pregnancy, some liquid can be seen under the skin in the neck area. During the ultrasound, the doctor measures the widest part of this so-called neck fold. The measured value gives an indication of a possible chromosomal abnormality, a heart defect, a diaphragmatic hernia or another malformation. Below 2.5 millimeters, the finding is considered normal. The greater the neck transparency, the higher the risk of possible fetal disease. However, a conspicuous finding in the neckfold measurement does not mean that your child necessarily has a chromosomal abnormality or malformation.

The result of the ultrasound examination (sonography) on the unborn child depends on the quality of the ultrasound device and the experience and skills of the gynecologist. Information about qualified practices and doctors in your area is available from the professional association of resident prenatal doctors (www.bvnp.de).

Taking into account the blood and ultrasound results as well as other risk factors (e.g. age and nicotine consumption of the mother), a computer program uses a specific algorithm to calculate how high the risk of a trisomy, another chromosomal abnormality, a heart defect or other malformations is. The mother's age is a very important influencing factor: the older the mother-to-be, the higher the likelihood of chromosome damage in the child.

Falsely positive results are quite common in the first trimester screening. This means that a critical value is determined, which is then not confirmed in the follow-up examinations.

First trimester screening: when is the right time?

As the name suggests, this prenatal exam is suitable for the first trimester of pregnancy. The test provides the best results between the 10th and 14th week of pregnancy.

First trimester screening: values conspicuous - what now?

If the first trimester screening shows an increased risk, your doctor will advise you to have further tests.

Advice on first trimester screening usually also includes information about a new test, the so-called prena test. With the recently available, also non-invasive method, it is possible to analyze fetal DNA in the mother's blood and in this way to gain further evidence of a chromosomal abnormality in the child. The blood sample is taken between the 12th and 14th week of pregnancy. It takes about a week to get the result. However, the options are also limited here. Trisomy 13, 18 or 21 can be detected with a relatively high degree of certainty using the prena test (between 92 and 99 percent). However, fetal malformations, developmental disorders, hereditary metabolic disorders, blood, skeletal or muscle diseases cannot be determined with it. False positive results are also possible.

If one of the non-invasive methods suggests a chromosomal abnormality or malformation in the child, ultimately only invasive methods such as chorionic villus sampling or amniocentesis can provide more precise information.

First trimester screening: yes or no?

There is a lot of discussion among experts as to whether or not first trimester screening makes sense. Most women hope that prenatal diagnostics will give them the certainty that their child is healthy. However, this guarantee cannot be given. The first trimester screening is not a diagnostic method, but only a statistical assessment of how high the risk of a chromosomal abnormality or malformation is. The result can only serve as a basis for making decisions about how to proceed further. Ultimately, every pregnant woman has to decide for herself whether she wants to have a first trimester screening carried out or not. In any case, there are no complications.

Tags: magazine foot care drugs