Amniocentesis
Amniocentesis is perhaps the pregnancy test that causes the greatest concern, as it is an invasive procedure—and the idea of a needle near the fetus is understandably stressful on its own.
What helps more than anything else at this moment is good information. To know exactly what happens, why it happens, and what to expect before, during, and after. That is the purpose of this page.
What is amniocentesis?
Amniocentesis is an invasive diagnostic test in which a small amount of amniotic fluid is taken from the uterus using a fine needle, under continuous ultrasound guidance. The amniotic fluid contains fetal cells, from which the fetus’s genetic material can be extracted and analyzed.
Unlike NIPT, which is a highly accurate screening test, amniocentesis provides a definitive diagnosis. It is the most reliable method we have to confirm or rule out chromosomal abnormalities and certain genetic conditions.
What does amniocentesis show?
By analyzing the amniotic fluid, we can investigate:
- Chromosomal abnormalities: trisomy 21 (Down syndrome), trisomy 18, trisomy 13, sex chromosome abnormalities, and other chromosomal disorders through a full karyotype
- Microdeletions and microduplications, which are not detected by a conventional karyotype, through molecular analysis (array CGH)
- Single-gene disorders, such as cystic fibrosis, thalassemia, and other inherited conditions, when there is a family history
- Infections – in certain cases, investigation of intrauterine infections
When is amniocentesis performed?
Amniocentesis is usually performed between the 15th and 20th week of pregnancy. The ideal time frame is around 16–18 weeks, when the amount of amniotic fluid is sufficient and the risk of complications is as low as possible.
It is mainly recommended when:
- The combined first-trimester screening or NIPT showed an increased risk of a chromosomal abnormality
- The second-trimester anatomy scan revealed a finding that requires further investigation
- There is a family history of a genetic disease
- The mother’s age or other factors increase the baseline risk
How is amniocentesis performed?
The procedure is performed in the clinic and takes a total of 15–20 minutes. The puncture itself is completed in just a few minutes. Step by step:
Before the procedure:
An ultrasound examination is performed to assess the position of the fetus, the placenta, and the amount of amniotic fluid, and to select the safest point for needle insertion.
During the procedure:
Under continuous ultrasound guidance, a fine needle is inserted through the abdominal wall and a small amount of amniotic fluid is withdrawn (about 15–20 ml). The needle does not approach the fetus. The ultrasound ensures its safe position at all times.
General or local anesthesia is not required in most cases.
After the procedure:
A brief ultrasound check is performed to confirm the fetus’s heart activity, and rest is recommended for the remainder of the day.
When are the results available?
This depends on the type of analysis:
- Rapid karyotype (FISH/QF-PCR): results for the main trisomies within 2–3 working days
- Full karyotype: results within 2–3 weeks
- Array CGH: results within 2–4 weeks
In most cases, the rapid karyotype is performed in parallel with the full karyotype so that there is an initial answer early on.
What are the possible complications of amniocentesis?
Amniocentesis is a safe procedure when performed by experienced hands, but like any invasive procedure, it carries a small risk of complications.
At our clinic, amniocentesis is performed by Dr. Maria Simou, Obstetrician-Gynecologist MD-PhD with specialization in Fetal Medicine, holder of the Fetal Medicine Diploma from the Fetal Medicine Foundation in London and Honorary Research Fellow at the Fetal Medicine Research Institute.
Possible—though very rare—complications include leakage of amniotic fluid, minor bleeding, or infection.
The risk of miscarriage is estimated at 0.1–0.3% in experienced centers—that is, about 1 in 300–1,000 procedures.
It is important to know that the physician’s experience and continuous ultrasound guidance significantly reduce these risks.
What should I watch out for after amniocentesis?
For the rest of the day, rest and avoiding strenuous physical activity are recommended. Most women return to their daily activities the following day.
Contact your doctor immediately if you notice:
- Leakage of fluid or bleeding from the vagina
- Severe cramps or abdominal pain that does not subside
- Fever above 38°C
- Reduced fetal movements
Frequently Asked Questions (FAQ)
There is some sensation, but it is rarely described as pain. Most women feel pressure or a pinching feeling during needle insertion—similar to a routine blood draw, sometimes a little more intense. The procedure is completed within a few minutes.
Most women feel mild cramps or a sense of heaviness in the abdomen for a few hours afterward, which usually settles by the end of the day. A feeling of fatigue or emotional tension is also very common. Waiting for the results is often harder than the procedure itself.
It is recommended that you keep at least the day of the test free. Most women return to their usual responsibilities the next day, provided there are no complications and the work does not involve strenuous physical activity.
Not always. If the NIPT is negative, amniocentesis is not needed in most cases. If the NIPT is positive, amniocentesis is the next step for definitive confirmation before any decision is made.
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