30. Chorionic villous sampling

Chorionic villous sampling was initiated in clinical practice in 1980s [29]. It is performed between 10 and 14 weeks. Placental biopsies are also done in second and third trimesters for rapid karyotyping.

#### 30.1. Technique

Prior to the procedure the crown rump length is measured to confirm the gestational age. Fetal heart activity is documented and a sample of villi can be obtained by the transcervical or transabdominal route [30].

#### 30.2. Trans cervical route

A special transcervical cannula developed by Rodeck with a malleable obturator is used. With a partially filled bladder, the gravid uterus is imaged transabdominally and the chorionic frondosum is identified. With the patient in lithotomy position a cannula is introduced through the cervical canal. The cannula guided into the chorionic frondosum under continuous ultrasound guidance. A 10 ml syringe with 2 ml of culture media is then attached to the proximal end of cannula. Suction is applied and a gentle to and fro motion of the cannula will ensure aspiration of villi into the medium in the syringe. The cannula is then withdrawn with continuous suction being maintained. The sample is then examined under a microscope to ensure the presence of branching villi. A minimum of 15 mg of tissue will be required for culture.

#### 30.3. Trans abdominal approach

placental margin. The amnion is pierced with a sudden controlled force, a jab of needle to prevent tenting of the membranes. The first few ml of fluid is discarded to minimize the contamination with maternal blood. About 20 ml of fluid is withdrawn for analysis. Not more

Individual sampling of both sacs using two different needles under direct ultrasound guidance can perform amniocentesis in twins. A single insertion technique in which needle is advanced

A blood stained aspirate can occur in 1–2% of the procedures. If the color is red, it indicates fresh blood possibly due to maternal blood contamination. Dark red or dark brown color of the fluid indicates prior intraamniotic bleed that is associated with poor fetal outcome. A brown color amniotic fluid can also indicate fetal aneuploidy. The overall pregnancy loss following

The incidence of fetomaternal hemorrhage is 63% in anterior placentas wherein the needle has traversed through the placenta. It reduces to 18% in posterior placentas. Hence, it is essential to determine Rh type of the mother prior to the procedure. Anti D immunoglobulin must always be given in rhesus negative women after any prenatal procedure. Fetal trauma is unlikely if the

Chorionic villous sampling was initiated in clinical practice in 1980s [29]. It is performed between 10 and 14 weeks. Placental biopsies are also done in second and third trimesters for

Prior to the procedure the crown rump length is measured to confirm the gestational age. Fetal heart activity is documented and a sample of villi can be obtained by the transcervical or

A special transcervical cannula developed by Rodeck with a malleable obturator is used. With a partially filled bladder, the gravid uterus is imaged transabdominally and the chorionic frondosum is identified. With the patient in lithotomy position a cannula is introduced through the cervical canal. The cannula guided into the chorionic frondosum under continuous ultrasound guidance. A 10 ml syringe with 2 ml of culture media is then attached to the

to the second sac after aspirating the first sac has been advocated by Jeanty.

than two insertions should be performed at one sitting.

procedure is done continuous ultrasound monitoring.

29.3. Amniocentesis in twins

96 Genetic Diversity and Disease Susceptibility

amniocentesis is estimated as 0.5%.

30. Chorionic villous sampling

29.4. Complications

rapid karyotyping.

transabdominal route [30].

30.2. Trans cervical route

30.1. Technique

Rodeck transabdominal chorionic villous biopsy forceps can perform transabdominal collection of fetal villi. A 20 Gauge spinal needle can also be used for sampling the villi transabdominally. The needle is advanced under ultrasound guidance and suction is applied as via the transcervical technique. A double lumen technique can also be used. In this, a large lumen outer needle is introduced into the uterus and a smaller gauge needle is passed through the outer needle to sample the villi. The advantage of this technique is that resampling can be done easily if the sample if insufficient in the first passage of needle. Transabdominal approach has been found safer with few complications than trans cervical route.

#### 30.4. Complications of chorionic villous sampling

Fetal loss can occur in 0.6–2% of cases. Loss rates are greater than 10% if more than two needle insertions are made to collect the chorionic villi. A sub chorionic hematoma may form in 4% cases, which usually resolves spontaneously. Chorioamniotis is a rare complication occurring in less than 0.3% cases. A delayed rupture of membranes can happen weeks to days after chorionic villous sampling in about 0.3% of cases.

The risk of fetomaternal hemorrhage is dependent on the amount of tissue aspirated and is detected by a rise in maternal serum alpha feto protein [31]. All Rh Negative non-sensitized mothers should receive a prophylactic Anti D immunoglobulin [32]. Perinatal complications like premature rupture of membranes, small for gestational age or intrauterine growth restriction have not been noticed after chorionic villous sampling. Chorionic villous sampling performed prior to 9 weeks of gestation is known to be associated with specific fetal malformations. Oromandibular limb hypo genesis syndrome and terminal transverse limb reduction anomalies have been documented when chorionic villous sampling was performed prior to 9 weeks of gestation. Chorionic villous sampling should not be performed prior to 9 weeks of gestation [33, 34].
