What is Cordocentesis?
Cordocentesis, better known as funiculocentesis, is an invasive diagnostic procedure, based on taking about 1-3 ml of fetal blood by puncture of the umbilical cord.
Compared to other invasive prenatal techniques, always aimed at collecting fetal biological samples (see amniocentesis and chorionic villus sampling), the funiculocentesis has a series of limitations that considerably restrict its field of use. In general, however, this examination allows the execution of analyzes useful for prenatal diagnosis, and represents a valuable tool for making intravascular fetal therapies.
How to do it
The examination begins with a preliminary ultrasound check, necessary to ascertain the fetal vitality, the gestational age and the best access to the umbilical cord.
Regardless of the access pathway, cordocentesis is performed under strict high-resolution ultrasound monitoring, using a 20-22 gauge needle inserted into the uterine cavity via the transabdominal route (puncture of the maternal abdomen, previously disinfected, sometimes under local anesthesia).
The puncture, independently of the site, is preferably carried out on the umbilical vein, the risk of fetal bradycardia associated with removal from the funicular arteries being greater.
After the extraction, the fetus is subjected to a further and harmless ultrasound check, in order to ascertain the absence of important bleeding at the puncture site, the formation of hematomas or thrombi (very rare) and fetal cardiac activity. In Rh negative women not immunized with Rh positive partners (see Coombs test during pregnancy) it is necessary to undertake seroprophylaxis with anti-D immunoglobulin, in order to avoid phenomena of fetal maternal incompatibility.
The greater invasiveness of cordocentesis compared to other methods of direct prenatal diagnosis, advises the execution in day-hospital regimen; alternatively, the procedure can also be performed on an outpatient basis, provided that complex therapeutic aids are readily available.
Indications
When is it performed?
The funiculocentesi is performed after the 18th week of pregnancy, typically between the 20th and 22nd week, the deadline granted by law 194/78 for voluntary interruption of pregnancy (provided that the continuation of the gestation represents a serious threat to mental health of the pregnant woman).
The abortion rate slightly higher than the other methods of invasive prenatal diagnosis limits the use of cordocentesis to cases in which the risk of disease is greater than the risk of abortion linked to the method. In particular, typical indications for cordocentesis are represented by:
- echographic suspicion of chromosomal anomaly found with morphological echography of the 20th week;
- need for a quick assessment of the fetal chromosomal outfit (5 - 7 days) to proceed to a possible abortion within the time allowed by law;
- late recourse to invasive prenatal diagnosis in patients with specific risks;
- failure of culture of amniocentesis, which on average occurs in 2 cases every 1000 samples (remember that amniocentesis is usually performed between the 15th and 18th week and requires up to three weeks for laboratory reporting);
- the presence of true mosaics in amniocentesis or chorionic villus sampling (that is the presence of cell lines with different chromosomal contents in the same sample, therefore potentially in the same individual: for example 46, XX / 47, XX +21, which could indicate a trisomy 21 in mosaic, see Down syndrome).
- diagnosis of fetal anemias (including that of maternal-fetal incompatibility), platelet diseases, hemoglobinopathies and hereditary coagulopathies; through cordocentesis it is also possible to perform transfusions in the uterus and to administer drugs and nutrients to overdeveloped fetuses;
- diagnosis of some congenital infections (less valid indication than in the past given the results obtainable with molecular biology techniques on amniotic fluid).
Cordocentesis is a free exam if performed for documented genetic risk or for a maternal age greater than 35 years.
| CVS | AMNIOCENTESIS | funiculocentesis | |
| Era (weeks) | 10-12 | 15-17 | > 18 ° |
| regime | Outpatient | Outpatient | Short, day hospital |
| Preparation of the patient | None. Blood group required. | None. Blood group required. | None. Blood group required. |
| Analyzed fabric | trophoblast | Amniotic fluid | Blood |
| Laboratory technique | 1) Cytogenetic investigations: direct and after cell culture 2) DNA analysis | Cytogenetic investigations after cell culture | 1) Cytogenetic investigations after lymphocyte culture 2) Serological, hematological analyzes etc. (specific cases) |
| Average response times | 1) Cytogenetic investigations: 3 days with direct technique; 3 weeks with culture 2) DNA: 2-3 weeks | 3 weeks (partial outcome possible in 2-3 days with FISH) | 1) Cytogenetic investigations: 3-5 days 2) Other analyzes: variable in relation to the type |
| Risks of abortion (%) | 0.5 - 2 | 0.5 - 1 | 2 - 3 * |
risks
Dangers for the Fetus
Normally, cordocentesis does not require the execution of local anesthesia and generally does not involve pain to the pregnant woman.
After sampling it is possible to observe an endamniotic blood dripping lasting a few seconds (35-40% of cases) on ultrasound, without this causing any risk to the fetus. Similarly, transient bradycardias are observed in 4.3% of cases, without any consequences for the fetus.
There are no maternal risks related to the procedure. The interpretation of the risk of fetal death related to cordocentesis is difficult; the statistical data, which show risk percentages of around 3%, are in fact taken with forceps, given that they are affected by the abortion not so much linked to the diagnostic procedure itself, but rather to the basic fetal pathology (in low-risk cases, for example, the incidence of fetal losses is around 2%). In addition to the gestational age (the risk decreases significantly if the funiculocentesis is performed after week 24), the risk depends on the degree of experience and skill of the operator, which requires the choice of doctors with proven experience in performing cordocentesis in centers reference specifications.
