Prenatal diagnostics - examination of the fetus

Prenatal diagnostics is used to obtain information about the health status of the fetus. Prenatal diagnostics can give information about the genetic characteristics of the fetus, anomalies or specific diseases.

Ultrasound examination of a woman

What is prenatal diagnostics?

Prenatal diagnostics is used to obtain information about the health of the fetus and about its genetic characteristics. Prenatal diagnostics can involve ultrasound examinations, or tests on samples from the placenta or amniotic fluid (amniotest).

It is also possible to obtain information about the characteristics of the fetus by analysing a blood-sample from the pregnant woman. This is called non-invasive prenatal testing (NIPT).
Prenatal diagnosis may involve a combination of tests, for example, ultrasound and NIPT or ultrasound and testing of a sample from the placenta.

If you consider prenatal diagnostics, you should contact your midwife or doctor early in your pregnancy. They will be able to give you more information. Prenatal diagnostic offered through the national health services requires a referral from your doctor.

Public healthcare during pregnancy is free of charge.

If you do not meet the criteria for NIPT through the public health care system, you can pay for this service from private healthcare.

Your decision about prenatal diagnostics

It is up to you to decide whether you want to have prenatal diagnostics or not.

You (and your partner) are encouraged to seek information about prenatal diagnostics before your first pregnancy check-up. This will make it easier to ask questions during your check-up.

Your midwife or doctor will give basic, neutral information about prenatal diagnostics at the first consultation, and they will be able to answer questions. This could give you a better basis to decide if prenatal diagnostics feels right for you.

If you need an interpreter, you should tell the clinic when you book your appointment.

If you choose to have prenatal diagnostics, you will have to consent in writing to the procedure.

Right to information 

Prior to the examination, you (and your partner) shall have information about different aspects of the prenatal diagnostics that is offered to you. You should be told about:

  • the purpose of the examination and about the procedure
  • what the examination can reveal and the possibility of getting unexpected information about the fetus
  • how long you will have to wait for the result
  • what will happen if the examination shows that your fetus could have a disease or anomaly, and the consequences such results could have for your fetus/unborn child, for you and for your family

When you have your results

If the examination shows that your fetus could have a disease or anomaly, you will receive more information about:

  • the disease or anomaly concerned
  • whether you will need to undergo further examinations to confirm the diagnosis
  • your options and rights, including follow-up and relevant support

You may be faced with dilemmas

You are encouraged to think through the possible dilemmas that you may have to face. Although most fetuses are healthy, some pregnant women will experience that the examinations reveal unexpected information about their fetus, e.g. that it could have disease or a major or minor anomaly.

If the results are inconclusive, you will be offered further examinations. You may have to wait a while before you have the result. This waiting period may be challenging.

Possibility for ultrasound scan during pregnancy week 11 to 14 and NIPT

All pregnant women will be offered an ultrasound examination in pregnancy week 11 to 14. The examination is offered through the public health services in all regions of Norway, and it is free of charge. Most pregnant women will have the ultrasound scan at their local hospital. You will receive more information about what your local hospital has to offer at your first doctor- or midwife consultation.

The NIPT-test

All pregnant women who are 35 or older at estimated date of delivery/ expected date of term (the due date) will also be offered a blood test (NIPT) that examines whether the fetus could have an extra copy of certain chromosomes (trisomy 13, 18 and 21). Pregnant women with specific risk factors will also be offered NIPT. NIPT through the public health services is free of charge.

If you are pregnant and younger than 35 on the due-date and there are no specific risk factors, you will not be offered NIPT through the public health services. You may contact one of the private clinics that is authorized to offer NIPT. You will be charged for their services.

More extensive prenatal diagnostics

Some pregnant women will be offered more extensive prenatal diagnostics at a Fetal Medical Centre.

You will be offered relevant prenatal genetic testing or ultrasound-examinations at one of these centres if

  • an ultrasound scan indicates anomalies in the fetus, or the NIPT-test indicates trisomy 13, 18 or 21
  • you have an increased risk of having a fetus with a serious inheritable disease or anomaly. Cystic fibrosis and spinal muscular atrophy (SMA) are examples of such diseases.
  • you or your partner previously had a child or fetus with a serious disease or anomaly

You can be referred to a Fetal Medical Centre and/or a Department of Medical Genetics by the primary health-care provider responsible for your pregnancy check-ups and by the local hospital.

If you (and your partner) are in a particularly difficult situation and will not be able to handle the burden associated with care for a child with a serious anomaly or condition, you can be offered NIPT, in addition to the ultrasound examination, at your local hospital.

Genetic counselling

You are entitled to genetic counselling if you know that there is a serious hereditary disease in your family or your partner's family, that could increase your risk of having a child with the same disease. The right to genetic counselling will also apply if you previously had a child with a serious disease or anomaly.

If you want genetic counselling, you will be referred to a university hospital with a Department of Medical Genetics / Fetal Medical Centre in your health region.

A healthcare specialist, normally a genetic counsellor or a specialist in medical genetics, will provide the counselling.

You will receive information about:

  • medical facts about the condition
  • the prenatal diagnostic procedure (s) that can be used to reveal whether the condition is present in the fetus
  • when you will get your result
  • the likelihood of having a child with the condition
  • if the fetus is affected, how the condition will develop/progress
  • the treatment options that are available

The ultrasound scan in pregnancy week 11-14

The ultrasound scan in week 11 to 14 will be done by a midwife or a doctor. The scan will show vitality of the fetus, estimate its age and the duration of the pregnancy, and examine the atonomy? of the fetus (head, arms, legs, belly, etc.) to have information about its development. Most fetuses have a normal development.

The ultrasound examination will also show the number of fetuses. If there are twins, it will be important to determine whether they share the placenta or not. Twins with a shared placenta need special follow-up during pregnancy.

The ultrasound scan can provide early information about certain serious conditions and anomalies in the fetus. It can also provide information about conditions in the fetus that need careful follow-up during the pregnancy.

The nuchal translucency (nuchal fold)

Between week 11 and 14 of pregnancy, there is a collection of fluid under the skin on the fetuses' neck – a nuchal translucency.

If the nuchal translucency is larger than expected, you can be recommended further tests to check for chromosomal anomaly or disease. Trisomy is a chromosomal anomaly. The fetus will then have an extra copy of chromosome 13, 18 or 21. The most common of these is trisomy 21, also known as Downs syndrome.

The likelihood for trisomy 13, 18 and 21 can be estimated by combining information about the nuchal translucency with further examinations of you and/or the fetus.

A large nuchal translucency can also be associated with other conditions, such as heart anomalies or certain genetic diseases. Fetuses with an increase nuchal translucency may also be completely healthy.

About the ultrasound procedure

The ultrasound examination is usually performed by moving a device over the skin of the belly, but an examination via the vagina will sometimes give a clearer picture.

The procedure does not hurt and will not harm the fetus. The entire procedure, including the information given by the midwife or doctor, takes about 45 minutes.

If the ultrasound examination shows that the fetus could have anomalies, you will be offered other examinations, usually at a Fetal Medical Centre.

If there are any signs of anomalies, it may be necessary to test a sample from the placenta or amniotic fluid, because the results of such tests can provide a diagnosis.

NIPT for trisomy 13, 18 and 21

A NIPT (non-invasive prenatal test) analyses DNA in a blood sample from a pregnant woman. The purpose is to obtain information about the fetus.

In all pregnancies, DNA from the placenta will be present in the blood of the pregnant woman. Analysing DNA from the placenta in the blood sample can give information about the genetic characteristics of the fetus, because the placenta and fetus usually have similar DNA.

A NIPT is used to examine whether a fetus has specific chromosomal anomalies: trisomy 13, 18 or 21. In some cases, NIPT may indicate an increased likelihood that the fetus has a trisomy. If so, you are advised to have an additional test, as a sample from the placenta or amniotic fluid to confirm a diagnosis.

Trisomy is a chromosomal alteration. The fetus will then have an extra copy of chromosome 13, 18 or 21. These are known as:

  • trisomy 13 (Patau's syndrome)
  • trisomy 18 (Edwards' syndrome)
  • trisomy 21 (Down syndrome)

NIPT is most precise for detecting trisomy 21. Trisomy 13 and 18 are rarer than trisomy 21. The NIPT-test is risk-free for both you and your fetus.

Who will be offered NIPT

All pregnant women are allowed to have a NIPT-test to check if their fetus could have trisomy 13, 18 or 21.

Pregnant women who will be 35 years or older when the baby is due, or with specific medical risk factors or social circumstances, will be offered NIPT via the public healthcare service.

If you are offered NIPT though the national healthcare services, the blood sample will be obtained when you have your ultrasound scan in pregnancy week 11 to 14.

You cannot have a blood sample taken for NIPT before week 10+0 of your pregnancy.

The public health services are not allowed to offer NIPT to determine the sex of the fetus (unless you have an increased risk for having a fetus with an X-linked disease, see below).

Who can offer NIPT?

Only service providers with an authorisation from the Norwegian Directorate of Health can offer NIPT and obtain blood samples for NIPT. The sample will be sent to a competent laboratory for analysis.

If you are 35 or older when the baby is due, you will be offered NIPT at your local hospital.

Health professionals working for service providers without the necessary authorisation are not permitted to obtain blood samples for NIPT.

Private health-care providers

Authorised private service providers can offer NIPT, but they are not authorized for other prenatal diagnostic procedures, such as the ultrasound scan in week 11 to 14 (described above).

Before the blood sample is taken, a midwife or gynaecologist will do a simplified ultrasound scan, limited to check that your fetus is alive, and to determine the number and estimate the age of the fetus(es)/pregnancy week. The scan will provide information of importance for the NIPT analysis.

The NIPT that is offered by private healthcare services is not covered by the national healthcare system (it is not free of charge).

Most authorised private providers use laboratories abroad (the Nordic Countries, EU or USA). The Directorate of Health requires that the laboratories work in compliance with European standards for data security (GDPR). The laboratories are not allowed to use the material or information they receive for any other purposes than the NIPT-analysis for trisomy 13, 18 and 21.

How long will it take to get the results from a NIPT test?

You will receive the results of your NIPT test within 10-16 days. Your doctor or midwife will contact you about results as agreed at the consultation.

The midwife or doctor will explain the results to you, how reliable/precise the test results are, and whether any further testing or examinations may be necessary.

In most cases, NIPT tests show no signs of trisomy in the fetus, and further testing will not be necessary.

What happens next if NIPT shows that the fetus could have a trisomy?

In some cases, NIPT may indicate an increased likelihood that the fetus has a trisomy. If so, you will be offered further examinations, such as a more extensive ultrasound examination, or an analysis of a sample from the placenta or amniotic fluid.

You will be offered follow-up at a Fetal Medical Centre. Hospitals and clinics that offer NIPT have procedures for referring pregnant women to a Fetal Medical Centre.

NIPT or NIPD for other medical conditions

NIPT for X-linked conditions

X-linked conditions are normally caused by mutations in genes on the X-chromosome and affect mainly boys.

You will be offered NIPT if there is an increased risk that you could have a child with a serious, hereditary X-linked condition. In such cases, NIPT is used to determine the sex of the fetus. If the disease could affect both girls and boys, you will be offered a placenta testing, an amniotest or NIPD.

Persons from families with X-linked conditions are often aware of the risk implied. Possibly, you had genetic counselling before you got pregnant.

If you are entitled to NIPT for determining the sex of the fetus, you will need a referral to a Department of Medical Genetics or a Fetal Medical Centre.

The NIPT-test for determining the sex of the fetus is very precise, but it cannot show whether the unborn child will have the condition or disease.

If the fetus is male, you will be offered a test of a sample from the placenta or amniotic fluid to check if the fetus has the genetic alterations that cause the condition. A test of a sample from the placenta or amniotic fluid will give a precise answer.

If the fetus is female, no further prenatal diagnostic testing will be necessary.

NIPD for conditions linked to specific genes (bespoke NIPD)

You may be offered non-invasive prenatal diagnostics (NIPD) if there is an increased likelihood of you having a child with a serious hereditary condition which is linked to a particular gene.

In most cases, the genetic alteration, if present, can cause a serious disease. NIPD could be offered if you or the child`s father have the genetic alteration in question (dominant inheritance) or if you both have it (recessive inheritance).

You will need a referral to a medical genetics' unit or a Fetal Medical Center. You have a right to genetic counselling prior to the test.

NIPD has been developed for several serious hereditary diseases linked to a single gene. The Department of Medical Genetics will know whether it is possible to offer you a NIPD instead of a test on a sample from the placenta or amniotic fluid.

The NIPD analysis normally must be “tailored" for the individual woman or couple.

Placenta test

A placenta test is an analysis of a sample of cells taken from the placenta. The placenta develops from the fertilised egg, and therefore reflects the DNA (genetic material) of the fetus.

A placenta test can show whether the fetus has a congenital disease or condition. Trisomy 13, 18 or 21 are examples of such conditions.

Who will be offered a placenta test?

You may be offered a placenta test if:

  • other prenatal tests have shown that there is a high probability of trisomy in the fetus
  • you have an increased risk of having a fetus with a serious, hereditary disease or condition
  • an ultrasound examination detected anomalies in the fetus

If you need a placenta test, you will be referred to a Department of Medical Genetics or a Fetal Medical Centre. You will have information and counselling prior to the procedure.

A placenta sample can be obtained after pregnancy week 11, most often between week 11 and 14.

What does a placenta test involve?

Placenta samples can be obtained in one of two ways:

  • through the abdominal wall (transabdominal)
  • via the vagina through the cervix (transcervical)

An ultrasound examination will be used to determine the best way to obtain the sample. This will depend on the position of the placenta.

Under ultrasound guidance, a needle is inserted into the placenta through the abdominal wall. The needle is used to draw a sample of tissue from the placenta.

Alternatively, a sample of tissue from the placenta will be obtained by a small tool or needle that is inserted via the cervix.

The procedure may hurt a little. The experience of pain varies from one individual to another. For most women, the pain is similar to the pain experienced when a sample of cells is taken from the cervix.

Afterwards, you may be asked to wait 15 minutes before leaving the hospital. You may be advised to relax a bit more than usual for two to three days after the procedure. Normally, you will not need to be absent from work.

How long will it take to get the results?

The time required to do the analyses and get the result will depend on the genetic test that is done. Most of the time, the results will be ready in 3 to 7 days. Some analyses take longer.

You will receive information about the expected time required for the analysis either at your genetic counselling session or when the placenta-sample is taken. You will be informed about the result in a letter or by phone.'

Exceptionally, the result of the analysis of the placenta sample is not accurate. In such cases - about two percent of the analyses - it may be necessary to double-check the result by a new analysis of a sample from the amniotic fluid (amniotest).

Are there any risks associated with the procedure?

Up to 0.5 percent of women who have a placenta test may experience complications caused by the sampling procedure, including miscarriage. Any miscarriage will usually occur in the first week after the sampling procedure.

Amniotest

An amniotest (amniocentesis) is an analysis of cells from the amniotic fluid. An amniotest can show whether the fetus has a congenital disease or condition. Trisomy 13, 18 or 21 are examples of such conditions.
An amniotic fluid sample will normally be obtained after the 15th week of the pregnancy, so a bit later in pregnancy than the placenta test.

Who will be offered an amniotest?

You may be offered an amnio test if:

  • other prenatal tests have shown that there is a high probability of trisomy in the fetus
  • you have an increased risk of having a fetus with a serious, hereditary disease or condition
  • an ultrasound examination detected anomalies in the fetus

If you need an amniotic fluid test, you will be referred to a Department of Medical Genetics or a Fetal Medical Centre. You will have information and counselling prior to the procedure.

The amniotic fluid sampling procedure is normally performed between week 15 and 16 of the pregnancy.

What does an amniotest involve?

Prior to the amniotest, you will undergo an ultrasound scan to determine the size and position of the fetus, and to find the best place to insert the needle.

Under ultrasound guidance, a thin needle will be inserted into the uterine cavity. Approximately 15 ml of amniotic fluid will then be drawn. This procedure may hurt a little, much like having a normal blood sample taken.

Afterwards, you may be asked to wait 15 minutes before leaving the hospital. You may be advised to relax a bit more than usual for two to three days after the procedure. Normally, you will not need to be absent from work.

How long will it take to get the results ?

The time required to do the analyses and get the result will depend on the genetic test that is done. You will normally have the results within 7 to 10 days. Some analyses take longer.

You will receive information about the expected time required for the analysis either at your genetic counselling session or when the sample is taken. You will be informed about the result in a letter or by phone.

Are there any risks associated with the amniotest?

Up to 0.5 percent of women who have an amniotest may experience complications caused by the sampling procedure, including miscarriage. Any miscarriage will usually occur in the first week after the sampling procedure.

Zanzu

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Content provided by The Norwegian Directorate of Health

The Norwegian Directorate of Health. Prenatal diagnostics - examination of the fetus. [Internet]. Oslo: The Norwegian Directorate of Health; updated Wednesday, November 9, 2022 [retrieved Monday, May 20, 2024]. Available from: https://www.helsenorge.no/en/undersokelse-og-behandling/fetal-diagnostics/

Last updated Wednesday, November 9, 2022