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Screening for Potential Risks: The Ins and Outs of Pregnancy Tests

Genetic disorders are a difficult situation for parents. Every parent wants a healthy child who will grow and thrive.

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While it is important to have information about your developing baby, it is your choice and your right to test. It is also your right to decide what you will do with the information.

7 What is Genetic Counseling?

Genetic counseling is learning about your options of having genetic tests to screen your developing baby for inherited disorders. It is also the process of making decisions after genetic testing. Counseling will give you the knowledge you need to make informed choices.

Genetic counseling involves meeting with a professional genetic counselor who can guide you through the counseling process and be your medical advocate with health care providers. The genetic counseling process first involves a discussion between you and your partner's medical and family medical history to discover if you or your partner has risks for genetic disorders. This is not only a discussion about your immediate family history but also your extended family medical history to understand if there are genetic risks.

You will also discuss former pregnancies and births, if applicable. Women who have genetic tests, such as amniocentesis or chorionic villus sampling, will discuss the results with a genetic counselor to understand the uncovered conditions.

Genetic counselors are trained to answer questions and concerns, and offer support to patients. However, the counselor should not give opinions on what the patient should do. Their job is not to sway a patient to specific actions after learning test results. It is the role of the genetic counselor to provide a safe place for the patient to make autonomous decisions without coercion.

6 How is a Genetic Counselor Trained?

A genetic counselor is someone who has special training to help patients make autonomous decisions about genetic testing. Genetic counselors are required to have a master’s degree in areas such as human genetics and counseling. They must go through continuous training to keep up with developments in genetics and counseling. This involves taking classes, and attending seminars about genetics.

As professionals, they need to have current knowledge of basic science, medical genetics, epidemiology, and counseling. Genetic counselors often belong to organizations that help them remain educated about advances in genetics and counseling. 

5 Family History

There are many reasons to talk to a genetic counselor. One important reason is if you, your partner, one or more of your children, or any other family member has a genetic disorder, birth defect, or developmental delay. Having a stillbirth, three or more miscarriages or a baby who died in infancy are other reasons for genetic counseling.

Experiencing more than three miscarriages does not always mean the causes are genetic. There are other reasons why women have miscarriages. Half of all miscarriages are genetic, but miscarriages can occur because of hormonal reasons. There may be blood-clotting, immunological reasons, or infections such as rubella. The reasons for miscarriage may be anatomical, as in a weak cervix, an irregular uterus shape, or large uterine fibroids.

4 Ethnicity and Genetic Counseling

Some genetic disorders are linked to specific ethnic groups. Often these groups lack the health insurance and coverage to have access to basic health care. They, through limited health care access, will not have the information necessary for well-informed genetic counseling.

The genetic disorder of sickle cell disease in African-Americans is an example of a disease that primarily strikes a medically undeserved minority population. The disease, while found in African-Americans, is found in other ethnic groups such as people from South and Central America, the Caribbean, Mediterranean countries, and India.

Sickle cell disease (SCD) is inherited when both parents have abnormal hemoglobin genes. Cells in the body need oxygen to survive and rely on hemoglobin in red blood cells to get oxygen from the lungs to all the tissues in the body.

Red blood cells with normal hemoglobin are disc-shaped, flexible, and can easily move through large and small blood vessels to deliver oxygen. However, sickle cell disease blood cell hemoglobin is shaped like a crescent or sickle-shaped. This makes the blood cells less able to move through small blood vessels to carry vital oxygen to body tissues. The sickle-shaped blood cells are rigid and can stick in small blood vessels. This can slow or block vessels, causing lack of oxygen to parts of the body.

Other ethnically linked genetic problems are the 32 genetic disorders affecting Ashkenazi (eastern and central European) Jews such as Tay-Sachs disease. Tay-Sachs is a rare genetic disorder that destroys nerve cells (neurons) in the brain and spinal cord.

Everyone has two copies of the Tay-Sachs gene (HEX-A). It is possible for a person to have one working HEX-A and a damaged HEX-A. This person will not show symptoms of Tay-Sachs, but he or she is a carrier. When two carriers have children, they pass along both damaged HEX-As to the child. This is how a child develops Tay-Sachs disorder.

It is a genetic disease that affects not only Ashkenazi Jews, but also specific French-Canadian communities of Quebec, people of Irish descent, the Old Order Amish community in Pennsylvania, and the Cajun population of Louisiana. Theoretically, it is possible for anyone who has damaged HEX-As to pass it along to his or her children, but these are the primary groups.

Many of these genetic diseases lack treatments. Preconception genetic testing and counseling, which should come with greater access to health care, can guide concerned couples on whether they can avoid these untreatable diseases in their potential children.

3 Age

Age is often a factor for genetic disorders, especially with genetic abnormalities such as Down syndrome. Women who have children too late in life risk having children with this disorder.

Down syndrome is more likely to occur with advancing maternal age because the woman's older eggs have a greater risk of improper chromosome division. A woman's risk by age 35 of conceiving a child with Down syndrome is about 1 in 400. At 40 years of age, her risk is about 1 in 100, and by age 45, the risk is about 1 in 30.

Normally, people have 23 pairs of chromosomes (called autosomes) and two sex chromosomes (allosomes). A new cell is formed at conception that receives one copy of each chromosome from the sperm and one copy from the egg. The new cell forms an embryo and then a baby. Each cell of the baby contains the same genetic material as the original 48 chromosomes with the same genes and DNA. Down syndrome babies have extra genetic material.

Instead of 46 chromosomes plus two sex chromosomes, there are 47 chromosomes. The most common error is three copies of chromosome 21, instead of two copies. This is true for about 95% of people with Down syndrome.

Other types of Down syndrome are translocation where an extra piece of chromosome 21 becomes attached to another chromosome and mosaic Down syndrome where a combination of cells with the normal number of chromosomes of 46 +2 mix with those that have a third chromosome 21 (47+2).

Mosaic Down syndrome can happen two ways. In the first way, the zygote has three 21 chromosomes, but during cell division, one or more cell lines lose one of the 21 chromosomes. In the second way, this variant of Down syndrome occurs when the zygote has two 21 chromosomes, but during cell division, one of the 21 chromosomes is duplicated. Children with mosaic Down syndrome may or may not have symptoms as serious as those with regular Down syndrome.

Translocation is a rare form of Down syndrome. In translocation Down syndrome, an extra copy of chromosome 21 is attached to a different chromosome. Both men and women can pass genetic translocation for Down syndrome to their children. There is also balanced translocation where the right amounts of chromosomes are in the wrong place.

Children with translation Down syndrome show many of the same cognitive and physical limitations of Down syndrome such as learning difficulties and heart disease. Balanced translocation children do not show typical Down syndrome effects, but may have trouble with miscarriage if they become pregnant.

2 Invasive Genetic Tests

There are several tests for genetic disorders, such as amniocentesis or chorionic villus sampling. There are other tests that are minimally invasive, such as nuchal translucency screening or, the newest form of genetic testing, NIPT.

Amniocentesis takes a sample of amniotic fluid (the fluid around your baby) from your uterus by inserting a thin needle through your abdomen and into your uterus. A small amount of fluid is withdrawn. Your body will make more fluid to replace the fluid and the baby will not be hurt during the procedure.

Some women feel slight cramping during or after an amniocentesis. You should rest after the test but most doctors will permit resumption of your usual activities the next day. The procedure is done to detect sickle cell disease, cystic fibrosis, Down syndrome, muscular dystrophy, Tay-Sachs and similar diseases. Risks, including miscarriage, are rare for the developing baby during amniocentesis.

1 Noninvasive Tests

Nuchal translucency scan (called the NT scan) uses ultrasound to measure the translucent space at the back of the developing baby's neck. Babies who have abnormalities like Down syndrome tend to accumulate more fluid at the back of their neck during the first trimester. The translucent space in a developing baby with Down syndrome tends to be larger than average.

Another sign is the lack of a fetal nasal bone. The ultrasound can also see major congenital heart problems. The test is done when you are between 11 and 14 weeks pregnant. It is often combined with a blood test that measures the level of alpha-fetoprotein, a protein made in the liver of a developing baby. A high level in your blood could indicate Down syndrome or other problems such as spina bifida. This test is often done with more blood tests, such as human chorionic gonadotropin (hCG), and a type of estrogen (unconjugated estriol, or uE3).

NIPT (Noninvasive prenatal testing) is a new blood test that quantifies chromosome disorders. The test involves a blood test that can help pinpoint the likelihood of your baby having disorders such as Down syndrome.

The test involves having a simple blood draw that measures the rate of abnormal fetal DNA in your bloodstream. When you are pregnant, fetal blood cells called cell-free DNA, or cfDNA circulates in your bloodstream. The blood draw can tell if there is a possibility of your baby having genetic disorders. The follow up test is more sophisticated, but invasive tests like chorionic villus sampling (CVS) or amniocentesis are necessary to make the results certain.

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