# Handbook of Genetic Counseling/Chorionic Villus Sampling (CVS)

Chorionic Villus Sampling (CVS)

## Introduction

* Discuss the reason for referral.
* Elicit prior knowledge about CVS.
* Elicit knowledge about AMA or other indications for session.
* Assess concerns and set goals for the session.
* Provide overview of topics for counseling session.

## Client & Partner Information

* Discuss why it's important to get pregnancy, personal, and family history.
* Go over pregnancy history:
** G?P?
** LMP? EDC?
** Infertility?
** Exposures?
** Medical complications?
** How has the pregnancy been going?
* Personal background:
** Occupation?
** Religion?
** Ethnicity?
** Chronic illness?
** Partner exposure?

## Elicit Family History

* Construct pedigree:
** Abnormal # miscarriages, stillbirths, infant deaths?
** Previous children with chromosome abnormality, NTD, Down syndrome, birth defects, mental retardation?
** Consanguinity?
** Other concerns/risk factors?

## What is AMA?

* Woman is age 35 & above at expected date of delivery.
* As maternal age increases, risks of birth defects increase.
* Women do not make new eggs like males make sperm.
* They are born will all the eggs they will have in their life and these eggs mature with age.
* There are procedures that can be done to assess the risk, but there are also risks associated with the procedures.
* The age of 35 is the "magic" number because this is when the risk of the procedure is justified.
* The background risk for major birth defects for women of all ages is 3-5%.

## Explain Chromosome Abnormalities

* Explain cells, chromosome, and DNA
* Show karyotypes
* Explain nondisjunction
* Show abnormal karyotypes (trisomy 13, 18, 21, sex chromosome anomalies)
* Give a general description of the clinical features and prognoses.
** Trisomy 18 & 13 are most severe with most affected dying before the age of 1 year
** Trisomy 21 is more mild; characteristic physical features and mild to moderate MR
** Turner and Kleinfelter's syndromes are sex chromosome anomalies. Also usually mild.

## Quote Risks

* Show charts to figure risk of chromosome abnormalities.
* Give age-specific risks:
** Age at CVS: ____________
** Down syndrome: 1 in _______ ( %)
** Any CA: 1 in ________ ( %)

## Discuss the option of CVS

* What is it?
** CVS is short for chorionic villus sampling
** The chorionic villi are wisps of fetal tissue or finger-like projections that attach the pregnancy sac to the uterine wall
** CVS is the technique in which this sample of placental tissue is obtained
** The technique has been around for approximately 15 years although methods have changed over time
** It is unique because it is used to diagnose certain birth defects in the 1st trimester of pregnancy rather than later in the pregnancy like amniocentesis
*** It is usually performed at 10-12 weeks gestation
* What can it tell me?
** CVS can detect certain abnormalities in the fetus
*** General chromosome abnormalities
*** Specific genetic disorders that have been previously identified
** It can determine the sex of the baby.
* What can it NOT tell me?
** CVS cannot detect neural tube defects such as spina bifida
*** For this reason, it may be useful to measure the amount of AFP in the maternal serum at 15-18 weeks gestation
*** Also, follow-up with US at 18-20 weeks is recommended
** It cannot detect all birth defects or mental retardation
*** For example, congenital heart defects, cleft lip & palate cannot be seen.
*** Also the severity of the defect cannot be known from CVS
* Exactly what does the procedure involve?
** Show figures of CVS
** Transcervical CVS:
*** Done at 10-12 weeks gestation
*** A speculum is inserted and the vagina and cervix are cleaned with betadeine
*** Some physicians apply a tenaculum to the lip of the cervix which can be painful
*** Using US to guide, a thin tube is guided into the placenta
*** Gentle suction is applied to the tube to remove the villi
*** This method is easiest to perform when the placenta is posterior and close to the cervix
*** A larger sample is taken as compared to transvaginal CVS
*** Discomfort is often minimal, perhaps similar to a pap smear
*** Post-procedure bleeding occurs in up to 10% of patients
** Transabdominal CVS:
*** Done at 10 weeks gestation or later
*** The abdomen is cleansed with betadeine
*** A local anesthetic injection may be given
*** Using US to guide, a spinal needed is inserted through the abdomen into the uterine wall and into the placenta
*** The needle is moved back and forth several times through the placenta
*** Suction is used to remove the villi sample
*** This method is easiest when the placenta is anterior or away from the cervix
*** This method is better for women with a retroverted uterus
*** A smaller sample (pieces of villi) is taken as compared to transcervical CVS
*** The procedure is usually more uncomfortable than the transcervical method
*** Bleeding after the procedure is rare
** CVS takes approximately 5-7 minutes (not including prep time)
** The baby's heartbeat is monitored by US
** The collected sample is examined under the microscope to confirm that fetal tissue and not maternal tissue was collected
** If maternal cells were collected, the CVS will be repeated
** The sample is sent to the lab
** Results are available in approximately 10 days
* What will it feel like?
** There may be some discomfort when the needle enters the skin and the uterus or when the catheter enters the cervix and placenta
** Some say that they feel pressure during the procedure
** You may experience a small amount of bleeding after CVS
* What are the risks?
** The background rate of pregnancy loss at 10-12 weeks is 2-3%
** CVS increases the risk of miscarriage by 1/100 (1%) in women with a normal uterus
*** Reinforce that 99% of women will have a healthy baby
** CVS increases the risk of miscarriage by 5/100 (5%) in women with a retroverted uterus using transcervical CVS
** Some studies indicate an increased risk for limb defects when CVS is done before 10 weeks gestation
*** When performed at 10-12 weeks, most recent studies do not report an increased risk because limbs have already formed at this point
*** The risk is approximately 1/3000 (0.0003%)
** There are special considerations for mothers who are Rh negative. They need to take RhoGam after the CVS procedure
** There is a low risk of uterine infection
** Exercise or strenuous activity is to be avoided for 24 hours after the procedure
** Sexual intercourse, douching, tub baths, or tampon use are to be avoided for 72 hours after CVS procedure
** CVS is not recommended for women with the following:
*** Cervical polyps, overly curved sampling pathway, active genital herpes (for trans-cer)
*** Interceding bowel, placenta too far from abdomen surface (for trans-abd)
*** Active vaginal bleeding or bleeding disorder
** You should notify your doctor if any of the following occur:
*** Fever greater than 100.4 F
*** Heavy bleeding or cramping
*** Amniotic fluid leakage
* Why should I choose CVS?
** CVS can be done earlier than amniocentesis (10-12 weeks versus 15-18 weeks)
** It may reduce a couples emotional stress if at risk for abnormality
** The procedure allows for termination at an earlier age
*** This is before the pregnancy is visible
*** Also before fetal movement is felt
** Allows for treatment of fetus affected with 21-hydroxylase deficiency
* Why might I not want to choose CVS?
** There is a higher risk for pregnancy loss as compared to amniocentesis
*** 1% for CVS versus 0.5% for amnio
** CVS does not detect NTDs
** CVS is less commonly done as compared to amnio
** With CVS, there is a greater likelihood of needing further invasive testing due to:
*** Laboratory failure
*** Insufficient sample
*** Maternal cell contamination
**** Seen in approximately 1.9% of cases
*** Mosaic or ambiguous results
**** There are 2 or more cell types that are different genetically
**** Seen in 1-2% of CVS cases

## Offer Resources

* Literature, contact info, etc.
* March of Dimes website

## Reporting of the Results

* If they are having the procedure, discuss how they would like to receive the results
** Appointment, phone call, etc.
** Who will contact them?
* Discuss the options: elective abortion, adoption, etc.