It involves a collection of amniotic fluid by means of a puncture with a fine needle through the abdominal wall under ultrasound control. Anesthesia is not necessary. You don’t need to be fasting.
The signature for informed consent will be required.
The pregnant woman must bring a copy of the blood group documented by a laboratory. Anti-D prophylaxis will be performed on Rh negative pregnant women.
At what gestational period can it be done:
It is performed on an outpatient basis around the 16th – 17th week of pregnancy.
How you do it:
After skin disinfection, a fine needle is introduced through the abdominal wall under ultrasound control. It causes a sensation comparable to that of an intramuscular injection.
What is it for:
It is mainly used to identify numerical and structural alterations of chromosomes (chromosomopathies). In cases where a chromosomopathy is diagnosed, the couple can request a therapeutic abortion, even after the third month, if the continuation of the pregnancy constitutes a danger to the physical and mental health of the mother (Law no. 194/78).
In which cases it is convenient to do it:
- maternal age equal to or greater than 35 years at the date of conception;
- increased risk from a combined screening test (bi-test and nuchal translucency);
- previous child with chromosomal abnormalities.
After the blood collection, the pregnant woman is invited to wait in a special room to rest for about 30 minutes. The day after the blood collection, the pregnant woman can return to normal work, avoiding intense work activity, sexual intercourse, long trips or sporting activity for at least a week.
Amniotic fluid will be examined in a cytogenetics laboratory. With the traditional technique, the incubation period, cell culture and mapping last at least 15 days.
In the event that the cytogenetics laboratory uses the so-called QF-PCR rapid test, the response will be communicated within two or three days from the date of collection.
THIS IS A FAST AND SENSITIVE METHOD FOR HIGHLIGHTING THE MOST COMMON CHROMOSOMAL ANOMALIES OF THE FETUS. IT IS APPLIED MAINLY ON AMNIOTIC FLUID WITHDRAWALS AND ALLOWS TO OBTAIN, IN THE ARCH OF 24-48 HOURS, THE QF-PCR (QUANTITATIVE FLUORESCENCE POLYMERASE CHAIN REACTION), THE RESULT CONCERNING POSSIBLE ANEUPLOIDIES OF CHROMOSOMES 21, 18, 13, X AND Y. THE ANALYSIS DIFFERENTIATES FROM THE TRADITIONAL CYTOGENETICS SURVEY THAT USES THE CULTURE OF AMNIOCYTES AND DETERMINATION OF THE KARYOTYPE, BECAUSE IT REQUIRES SMALL SAMPLE QUANTITIES (1 ML) COMPARED TO 19-20 OF THE CLASSICAL AMNIOCENTESES. THE QUICK PERFORMANCE OF THE QF-PCR ALLOWS TO REDUCE THE REPORT WAITING TIMES TO A MINIMUM.
Amniocentesis, as everyone knows, is an invasive examination which, although minimal, involves a certain risk. The patient or rather the couple must be informed exactly what it is.
- late abortion: 0.5% – 1%;
- loss of LA after collection: approx. 2%;
- Endouterine infections: 0.5%;
- Fetal lesions: very rare;
- Diagnostic errors: very rare, 1 in 500 amniocentesis. They can involve either the failure to identify a chromosomopathy (fetal mosaicism or contamination of maternal cells) or a false positive (cormosomal aberrations arising “in vitro” during culture).
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