Prenatal diagnostics

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Foetal diagnostics means that the foetus is examined for illness or developmental deviations. It is also possible to calculate the risk for this.

Only about 1% of all children are born in Norway with serious developmental disorders or illness.Foetal diagnostics is a service that is only given by a maternal-foetal medicine specialist at the University Hospital and is given to pregnant women who:

  • Signs of developmental abnormalities in the fetus have been detected by an ultrasound examination or by proven “high risk” at NIPT. (We at oslo jordmor- og ultralydklinikk (OJUK) refer the pregnant woman to extended fetal diagnostics in case questions of deviations)
  • Are 35 years or older at due date. This is because the risk of chromosome failure increases with maternal age.
  • Previously given birth to a baby or foetus with a developmental disorder or serious illness.
  • Increased risk of serious illness in the foetus if the condition can be detected, including hereditary diseases.
  • Uses medications that can harm the foetus.
  • Have been shown signs of developmental disorders in the foetus during an ultrasound examination.

Voluntary examination

Jordmor med Ultralyd bildeIt is important to be aware that this is a voluntary examination and the pregnant woman can decide for herself whether or not to take advantage of the offer. It is also the pregnant woman who decides what she will do if it turns out that the foetus has a developmental disorder.

Therefore, it is very important in advance to consider what such an examination might uncover and further on what she will do if the foetus has a developmental disorder.

If the criteria for foetal diagnosis are met and the examination is desired, the pregnant woman can contact the midwife or doctor, preferably 8 weeks after the last menstrual period.

The midwife will refer her to the department of medical genetics at the University Hospital. It is recommended to bring the partner/spouse.

In the hospital, the couple will receive information about which examinations can be performed and what risks they entail. The couple also gets information on how the tests are done, what answers they can give and how big the probabilities for any findings are.

After this conversation, the woman will be referred for further investigations according to her wishes.

The varius foetal diagnostic examinations

1. KUB-test/Risk assasment

In hospitals in Norway since 2021 the KUB test is replaced with an ultrasound-examination and NIPT.

KUB- test stands for combined ultrasound and bloodtest. It is a calculation of risk and it is done by taking a blood sample of the pregnant woman in weeks 10–11. In addition, an ultrasound examination is carried out in pregnancy weeks 11–14 where the foetus is examined to look for chromosome abnormalities, including Down syndrome (trisomy 21), Pataus syndrome (trisomy 13) and Edward syndrome (trisomy 18).

Increased fluid retention in the neck and small nostrils are markers that can indicate chromosome abnormalities. The risk increases with the size of the fluid collection behind the neck and the age of the pregnant woman. The risk of chromosomal abnormalities increases with maternal age. By combining the findings in these studies, the risk of chromosome failure is calculated.

This risk assessment is harmless to the foetus but does not provide an equally accurate result as with samples taken from the placenta or the amniotic fluid. From the result of the examination, the pregnant woman determines if she wants a diagnostic test. If the risk is bigger than 1:250 (0,4%) for the foetus to have trisomy 13, 18 or 21 the doctor will discuss options for further investigations, as a samle from the placenta or amniotic fluid, or NIPT-test.

2. Sample from the placenta or from the amniotic fluid 

Is done by taking samples from the placenta at 11 completed weeks of pregnancy or from the amniotic fluid at 15 completed weeks. The doctor pierces a thin needle through the stomach and into the uterus. Amniotic fluid or tissue is sucked from the placenta through the needle and here, chromosome errors can be detected. This test gives an accurate result of a cromosonal abnormality. The probability of abortion is approximately 0.5%.

Many pregnant women, therefore, choose to do this examination only if the risk assessment shows a high probability of illness in the foetus. The answer is ready after 2–4 weeks. The test is usually not painful but this differs from person to person. It can be compared to having a blood test.

If the examinations show illness or developmental disorders in the foetus, foetal diagnostic experts will provide thorough information on the developmental disorder and the illness the baby will have, as well as treatment options and support measures.

3. NIPT-test

NIPT (non – invasive Prenatal Test) is a relatively new test who is used in feotal Diagnostics. The bloodtest is is done by taking a blood sample of the pregnant woman in weeks 9–11. In the pregant womans blood there are pieces of the fetus DNA. One assume that the genetic material  comes from cells that grows in the uterine wall, and therefore get in contact with the blood. Since the placenta is from the same genetic origin as the foetus, it often (but not always) have the same cromosome origin as the foetes. Therefore in principal the whole genetic material (DNA) can be mapped out before the baby is borned. NIPT is a risk assasment. NIPT is today in Norway a secondary test, wich is done only if KUB-test show high probabilityof cromosme abnormalities.

If the woman wants to terminate the pregnancy, there is free abortion until week 12. After this, an abortion will be granted after applying for it, depending on the severity of the illness. The woman is not required to terminate the pregnancy if she does not want to, regardless of what the examination shows.

The woman chooses what is right for herself.

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