Chorionic villus sampling are an invasive diagnostic procedure that involves obtaining chorionic villi of the placenta.
It is relatively recently been introduced in the late 80s, and now become a routine technique.
WHAT ARE THE INDICATIONS FOR CHORIONIC VILLUS SAMPLING?
- If the biochemical screening provides a combination of high risk (1 / 250) for trisomy 21 (Down syndrome) or trisomy 18 (Edwards syndrome).
- If there was a chromosomal abnormality in a previous pregnancy.
- If there is a chromosomal abnormality in both parents.
- If a change occurs in the fetal ultrasound in the first quarter.
- To confirm the diagnosis of pre-implantation, after implantation of one or more embryos in assisted reproductive technology.
- In case of differences of more than a week between twins, diagnosed early by ultrasound measurement of the length of the embryo.
- For the genetic study after an abortion when there are more previous abortions.
2.-Monogenic disease with molecular or biochemical diagnosis.
Chorionic villus sampling is currently considered the preferred technique for studying chromosomal abnormalities and inherited diseases in the first quarter.
HOW AND WHEN PERFORMING CHORIONIC VILLUS SAMPLING?
The chorionic villus sampling is done between weeks 10 and 14. The levy can be done through the cervix by transcervical (between weeks 10 and 14) or transabdominal between weeks 11 to 14.
You must run the asepsis of the vulva and vagina. It introduces a vaginal speculum and the cervix is localized. We introduce a semi-rigid forceps through the cervix and leads to (placenta) and through a continuous ultrasound guidance is extracted a sample of chorionic villi.
You can make an aspiration of chorionic villi aspiration cannula through a rigid or flexible.
TRANSABDOMINAL: It makes an asepsis the abdominal wall and after a guidance under local anaesthesia. Cross this with a trocar to reach the placenta under continuous ultrasound guidance. Trocar is introduced through the clamp until you reach the villi from which the sample is extracted.
It can also be performed with suction syringe technique.
The choice of this or that technique, transcervical or transabdominal, depending on the experience of every gynecologist, although the amount of sample obtained with the transcervical is usually higher than transabdominal
It is recommended to rest after chorionic villus sampling from 24 to 48 hours.
Should be given anti-D immunoglobulin to all pregnant women with Rh negative within 72 hours.
1.-Should not be performed before 10 weeks because it has been associated with limb defects, with shortening of the limbs themselves.
2.-Patients seropositive for HIV, hepatitis B and hepatitis C with high viral load.
These contraindications are not absolute, since each case must be studied, again emphasizing that there are more benefits to both mother and fetus.
In 2% of cases the results are inconclusive, and it is proposed that a study of amniocentesis and amniotic fluid.
The result is slow to arrive in 48 hours.
WHAT ARE THE COMPLICATIONS OF CHORIONIC VILLUS SAMPLING?
The most common complications are bleeding from the vagina if it is realized by transcervical and abdominal pain in the puncture site, in case you have performed a transabdominal sampling. There is a small risk (1%), premature rupture of membranes and infection of the amniotic fluid and membranes (chorioamnionitis).
The risk of miscarriage decreases with the experience of the team that executes it is currently less than 1%.
Some studies indicate that the risk of miscarriage is similar to chorionic villus sampling performed by trans cervical to that performed in the amniocentesis.