Amniocentesis: when it is done, what is the cost, what are the risks

Diagnostic investigations to identify malformations of the fetus

For the search for possible malformations of the fetus, currently the prevailing orientation is to advise pregnant women in the first trimester of pregnancy to perform,

  1. at about the twelfth week of pregnancy  , two tests called “combined test of the first trimester” consisting of an ultrasound of the nuchal translucency (NT), and in a Duo-test (or Bi-test), which estimate the probability that the fetus is suffering from chromosomal malformations
  2. at about the thirteenth  /  fourteenth week of pregnancy  , to take a fetal DNA test to identify any genetic abnormalities;
  3. at the fifteenth  /  sixteenth week, to possibly undergo an amniocentesis if the DNA test is positive.

In this article we will focus in particular on amniocentesis.

The amniocentesis

Amniocentesis is an invasive prenatal diagnosis technique, which consists in taking a small quantity of the amniotic fluid that surrounds and protects the fetus in order to obtain biological samples useful for a prenatal diagnosis.

It is done to verify whether or not certain types of defects exist in fetal development, such as  Down syndrome , which is precisely a chromosomal anomaly (a genetic condition characterized by the presence of an extra chromosome in the cells).

Amniocentesis – which has an accuracy of about 99.4%, which means that it gives us almost certain results – presents some risks, albeit slight, for both the mother and the baby.

When it is prescribed

Amniocentesis is usually prescribed for women,

  • who have a significant risk of transmitting genetic diseases,
  • who have obtained   abnormal results from “normal” ultrasound scans ,
  • who have a family history of certain birth defects ,
  • who have already had children or pathological pregnancies.

What it can detect

Amniocentesis does not identify all possible congenital defects , but it can be used to identify conditions with significant genetic risks in relation to (for example):

  • at Down syndrome;
  • all’anemia drepanocitica;
  • to cystic fibrosis;
  • to muscular dystrophy;
  • to Tay-Sachs disease (which is characterized by mental retardation) and the like.

Amniocentesis can also identify certain neural tube defects (these are diseases in which the brain and spinal cord do not develop properly), such as spina bifida (incomplete closure of one or more vertebrae) and anencephaly. (unborn child without the cranial vault and the brain).

It is done in conjunction with an ultrasound scan , which can detect birth defects not detected by amniocentesis (such as  cleft palate ,  cleft lip , clubfoot, or heart defects).

There are, however, some birth defects, which are not detected by either amniocentesis or ultrasound .

If you are going to have this procedure, you may also ask to know the sex of your baby. Amniocentesis is in fact the most accurate way to determine the baby’s gender before birth.

An amniocentesis may also be performed during the  third trimester of pregnancy   to determine if the baby’s lungs are mature enough for delivery, or to evaluate the presence of infections in the amniotic fluid.

In addition to the amniocentesis, the other test that allows us to study the chromosomal heritage of the fetus is  CVS .


Contrary to amniocentesis, which is a rather simple sampling procedure, CVS is performed by expert operators, in high-level specialized centres, who take a sample of placental tissue through the vagina or abdomen.

CVS (chorionic villus sampling) is a procedure aimed at taking fragments (10-15 mg) of chorionic tissue to be examined in the laboratory in order to obtain information on possible diseases of the fetus.

It is usually done earlier: even six weeks before the amniocentesis, towards the  tenth  /  twelfth  week of pregnancy.

However, with CVS, the risk of miscarriage is double that with amniocentesis. Furthermore, the examination of the samples taken by CVS does not give equally precise results.

For further information on CVS, we refer you to  this article .

How an amniocentesis is performed

Here is – in brief – how amniocentesis is performed:

  • A full anatomical ultrasound is performed first.
  • Then, in preparation for the amniocentesis, a small area of ​​the abdomen is cleaned with an antiseptic.
  • You may ask for a local anesthesia (pain reliever) to reduce any discomfort.
  • First, the doctor locates the location of the fetus and placenta with ultrasound.
  • Then – under ultrasound guidance – he inserts a thin hollow needle through the abdomen and uterus, far from the baby, into the amniotic sac .
  • With the needle withdraw a small amount of liquid (less than 30 ml).
  • During this procedure, and up to a few hours afterward, you may experience minor menstrual-like cramps or discomfort.
  • The collected liquid is then sent to the laboratory for analysis.
  • Multiple tests can be performed on a single amniotic fluid sample, depending on the genetic risk and the reasons why the test was prescribed/desired.

When can it be done?

Depending on the reasons and the period in which this screening procedure is carried out, we can speak of early amniocentesis, very early amniocentesis, late amniocentesis.

early amniocentesis

very early amniocentesis

  • This is done as an alternative to chorionic villus sampling before the fifteenth week .

late amniocentesis

  • The late one is done after the  twenty-fifth week , when certain conditions occur that require a sample of amniotic fluid.

Its risks

There is a slight risk that the amniocentesis will cause an abortion (less than 1% of cases, approximately: between 200 and 400 tests one case occurs).

Other possible complications that may occur are damage to the baby or mother, infections and premature births, but these are extremely rare cases.

Post amniocentesis rest

After an amniocentesis, you should go home and relax for the rest of the day.

You should also avoid physical activity, especially if it is strenuous.

You should avoid lifting anything heavier than 10 kilograms and having sex.

To relieve pain, you can take two doses of  Tachypirine / paracetamol every 4 hours.

The day after the amniocentesis you can resume all your normal activities, unless otherwise indicated by your doctor.

Call your doctor if, after an amniocentesis, you have a fever or if you notice vaginal discharge/bleeding, or if you feel abdominal pain more intense than normal cramps.

Its costs

The National Health Service gives women of any age the opportunity to undergo free amniocentesis,

  • if they are positive in the combined test for Down syndrome (Tritest)
  • or if they have a high risk due to family conditions.

In other cases, the cost of the amniocentesis, which ranges from approximately 600 to 900 euros, is borne by the pregnant woman.

His results

The results of the amniocentesis are usually available within 2-3 weeks of the collection.

Amniocentesis yes – amniocentesis no

Although most of the conditions that are detected with this procedure cannot be cured, one reason for doing this test is that it lets you know about them beforehand.

This way, parents have time to make decisions about future care for their baby, or to make the difficult decision to terminate the pregnancy.

However, bad news rarely emerges. More than 95% of the time an amniocentesis turns up nothing but a healthy baby.

Also, if you choose to know your baby’s sex with this test, you’ll have a great advantage in decorating his room and buying the right clothes.

Complications caused by this procedure are also rare. But they do happen. So before deciding to do it, they should be considered.

It should be taken into account, for example,

  • that about one in 100 women notices small leaks of amniotic fluid from the vagina or from the point where the needle entered, and that you too may bleed slightly: all of this will most likely stop after a few days;
  • that there is even a small possibility of abortion (it happens from one case out of 400 to one out of 200);
  • that about one in 1,000 has uterine infections, and that these too could lead to miscarriage.

Only you and your partner — with your doctor’s advice — can decide whether these risks outweigh the benefits of testing.

Katherine Johnson, M.D., is a board-certified obstetrician-gynecologist with clinical expertise in general obstetrics and gynecology, family planning, women’s health, and gynecology.

She is affiliated with the Obstetrics and Gynecology division at an undisclosed healthcare institution and the online platform,

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