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Amniocentesis

Amniotic fluid test is a fetal diagnostic examination. An amniotic fluid test can ascertain with great certainty whether the fetus has chromosome disorders, such as Down syndrome (formerly called Mongolism), or more severe forms of spinal hernia.

Amniocentesis

At special issues, it is sometimes also possible to detect a fairly large number of very rare hereditary diseases. Amniotic fluid tests are performed when there is an increased risk of these diseases in the fetus. A normal amniotic fluid test does not guarantee that the fetus is healthy from other points of view.

What is fetal diagnosis?

Fetal diagnosis in a broad sense means all the various checks performed throughout pregnancy at the Midwife Reception (MVC). Checks are performed to ensure fetal health. However, what are commonly called fetal diagnostics are more specific studies such as:

  • Ultrasound at 15-20 weeks of pregnancy.
  • Directed ultrasound.
  • Benchmarking methods for assessing probability of Down syndrome:
    CUB
    NUPP
    Late blood test.
    Ultrasound 15-20 weeks.
  • Amniocentesis.
  • Chorionic villus sampling.

For which women can amniotic fluid test be relevant?

An amniotic fluid test can be offered to women under the following conditions:

  • Women who were 35 or older when they became pregnant.
  • Parents who have previously had children with Down syndrome or other chromosome disorder.
  • Parents who in previous investigations have shown themselves to have a chromosome change.
  • In some cases, abnormalities in the fetus that can be suspected to be caused by chromosome disruption have been detected in a standard ultrasound examination.
  • When the woman is considered to be at risk, taking into account established risk assessment methods.
  • Parents who have previously had a child with spinal cord hernia or similar brain malformations or themselves have or have had spinal cord hernia.
  • Parents who have previously had children with hereditary metabolism disorder.
  • Parents with genital hereditary illness, such as hemorrhagic disease, in the genus.
  • The woman requests it because she is worried that the child may have a chromosome abnormality.
  • Amniotic fluid tests are sometimes required to examine and treat other conditions during pregnancy, such as Rh immunization. In these cases, the amniotic fluid is analyzed to detect substances in the fluid itself, and not just to look at the child's chromosomes.

Information about the amniotic fluid test is provided by the doctor and / or midwife where the pregnancy is controlled. However, the final decision whether or not to undergo sampling is the woman's own, if she belongs to any of the above groups.

What analyzes are performed?

In the vast majority of patients, two types of amniotic fluid are performed: chromosome examination to exclude chromosome disorder and AFP examination to exclude spinal cord hernia.

When is the test taken?

The sample is taken approximately during pregnancy week 15, as there is so much amniotic fluid that some can be sucked out for examination.

How is amniocentesis done?

Prior to sampling, a thorough ultrasound examination is performed to find the best sampling site and avoid the fetus and placenta. The doctor then, under ultrasound control, inserted a thin needle through the abdominal wall and the uterine wall into the fetal sac and sucked out about 15 ml of amniotic fluid. The procedure is done without any form of stunning. The mother may feel a slight discomfort, but by and large, the sampling is virtually painless. The fetus is unaware of the procedure.

The prospective mother does not have to be housed, but can go home the same day. Heavy lifting should be avoided in the next few days after sampling. The amniotic fluid sample is sent for chromosome analysis to the nearest clinical genetics laboratory.

Women with Rh negative blood group (one in eight women have this) receive a gamma globulin (anti-D) syringe to prevent antibody development. Anti-D is also given to some mothers after childbirth, depending on the Rh factor the newborn has. The use of anti-D is a great medical success.

Are there any risks with the procedure?

The risks are considered to be very small if the procedure is performed in connection with an ultrasound examination. However, miscarriages have been seen within the next few weeks, which may have had to do with sampling. The general incidence of miscarriage is usually about 1-2 percent in pregnancy week 13-15. For women who have undergone amniocentesis, this is stated to be about 0.5 percent higher, partly because these women themselves constitute a risk group.

How long does it take to know the result?

Answers to all age-dependent chromosome abnormalities, ie Down syndrome, trisomy 18 and 13 can generally be provided within a week. When measuring AFP, it takes about a week for response. The answer is sent by letter from the doctor who performed the amniotic fluid test. Answers to complete chromosome analysis usually take 3-4 weeks. If the test is normal, you will receive an answer directly from the laboratory.

How reliable is the result of an amniotic fluid test?

There are very few things in life that can be guaranteed to 100 percent. Also, fetal diagnostics (amniotic fluid testing and ultrasound examination) provide no hundred percent guarantee that the expectant child is healthy in all respects.

What if the test shows something abnormal?

Should the chromosome examination or AFP examination show anything abnormal, the doctor who performed the sampling will receive a response and contact the parents directly for discussion. Some chromosome abnormalities can cause very serious damage, while others can be completely harmless. Sometimes, if more unusual or complicated diseases are found, consultations with the genetic laboratory may be necessary.

If the AFP value is high, it may indicate spinal cord hernia or other similar disease in the fetus. In the first instance, a new ultrasound examination is done with special focus on the fetal spine, brain and abdominal wall. Should this ultrasound examination be found to have serious damage to the fetus, or if the chromosome examination shows abnormalities, it may be necessary to interrupt pregnancy. It is a decision, however, that can only be made after careful discussion and advice. It is therefore important that the parents decide beforehand on how to do if the test should show serious changes.

 

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