Genetic Testing and Pregnancy

For couples in the process of trying to conceive, or if they are already expecting, they may begin to consider genetic testing. This is the process of one or both parents having blood drawn to look for any abnormalities. Genetic testing is often done to determine if the parents may have the possibility of giving their child a genetic disease. Since these diseases are recessive disorders, both parents must pass on the gene in order for the child to be affected. If one parent tests positive while the other tests negative, there is no possibility of the child being affected. However, there is a 25% chance that the child will inherit a genetic condition if both parents test positive for the recessive genes.

Oftentimes women will be tested first, simply because they visit their doctor more often, especially during pregnancy or immediately prior to conceiving. Once the results are received, if the woman has no genetic abnormalities, there is typically no reason to test her partner.

Genetic Testing and Pregnancy

  • Blood test

This is the simplest of the three options for genetic testing, and considered relatively simple. If you are worried that your child may inherit a genetic disorder, especially if there is one in either yours or your partners’ medical history, then doing this testing will determine the likelihood on if your child will inherit the disorder. Typically done at your first OB appointment, a nurse will simply draw some blood, have it sent to the lab for analysis, and then call with the results in a couple of weeks. Depending on the results, you may have nothing to worry about, or your doctor may suggest other tests to determine if any genetic disorders may be inherited.

  • Chorionic villus sampling

Typically performed between the tenth and twelfth week of being pregnant, Chorionic villus sampling involves removing a small piece of the placenta. After doing so, the doctor will examine the piece and determine if any genetic issues are present in the womb. Unfortunately, due to it being an invasive test, completing chorionic villus sampling has been known to cause miscarriages.

  • Amniocentesis

Only carrying a small risk of causing a miscarriage, amniocentesis involves using a hollow needle to take a small portion of amniotic fluid. By doing so, usually between fifteen and twenty weeks, the doctor will be able to determine not only if there is the presence of a genetic disorder, but also be able to determine the maturity of the lungs as well as the sex.

What Are the Benefits of Genetic Testing During Pregnancy?

For prospective or expecting parents, there are many reasons they may consider genetic testing, and why their doctor may recommend it as well. Although most babies are healthy at birth, there are still 3-5% of children born with birth defects. Fortunately, many of these defects can now be detected, especially when they are due to either genetic disorder or syndromes.

While it may be difficult to come to the realization that a child will be born with a genetic disorder, it can actually help prepare a family both mentally and physically by dealing with any guilt, mourning for the unhealthy child and even contacting a genetic counselor to find a support group. Additionally, knowing ahead of time will allow families to make the appropriate preparations for when they bring the child home, and understand better how to raise the child depending on the genetic disorder they inherited.

Common Birth Defect

Along with knowing that a child has a genetic disorder, doctors can also pinpoint what disorder was inherited among the four thousand known birth defects, either mental or physical. The child may have inherited a disorder that is very mild and easily reversed, while others may suffer from something fatal. Fortunately, most prenatal screenings will detect these, but not all birth defects can be detected.

The following list describes the most common birth defects, along with how many they affect in the United States:

  • Only 1 in 940 babies suffer from cleft lip and/or palate
  • 1 in 775 suffer from clubfoot
  • 1 in 3,200 suffer from cystic fibrosis
  • 1 in 769 suffer from down syndrome
  • From 1 in 667 to 1 in 5,000 suffer from fetal alcohol syndrome
  • 1 in 4,000 males and 1 in 6-8,000 females suffer from fragile X syndrome
  • 1 in 100 suffer heart defects
  • 1 in 10,000 suffer from Huntington’s chorea
  • 1 in 1,996 suffer from hydrocephalus
  • 1 in 15,000 suffer from phenylketonuria (PKU)
  • 1 in 500 African American children suffer from sickle cell anemia
  • 1 in 3,000 suffer from spina bifida

Who Should Get Genetic Testing?

From Ethnic Perspective

Not everyone will need to consider genetic testing, but depending on your ethnicity, it may become a considering factor. The following list discusses on who should consider genetic testing, and what they may be more prone to than others.

  • European Caucasians need to test for cystic fibrosis
  • Eastern European Jews need to test for cystic fibrosis, Tay-Sachs, Canavan, and others, including familial dysautonomia
  • African Americans and Mediterranean descent need to test for sickle cell anemia and thalassemia
  • Southeast Asian descendants need to test for thalassemia
  • French Canadians should test for both Tay-Sachs and cystic fibrosis

Considering Genetics and Pregnancy History

  • One parent, or a close family relative, has the disorder

Since genetic disorders are recessive, parents may both harbor the genes for it without knowing they do since it has never manifested in them. This occurs because one parents passed on a normal gene, while the other passed on an abnormal gene, making the future parent have a 50% chance of passing on the problematic gene. If one of the parents, or a close relative, has inherited the disease, they will need to get tested.

  • One child already affected

While many birth defects are caused by genetic anomalies, some can occur from exposure to harmful chemicals, an infection during pregnancy or any form of physical trauma. The true cause of birth defects is not yet known and can stem either from the parent’s cells, or an error in the child’s cells as it is being formed in the womb.

  • Two or more miscarriages

Spontaneous miscarriages are typically caused by significant chromosome issues. If a mother has had multiple miscarriages, it may mean there is a genetic issue.

  • Giving birth to stillborn child with evidence of genetic disorder

Some of the more serious genetic illnesses cause abnormalities in a child’s physical appearance.

  • Mother is 34 years old or older

As a woman gets older, her risk of having children with chromosomal problems, such as trisomy, greatly increases. At the same time, older fathers may father a child with a new dominant genetic mutation that was not previously present in the family.

In order to gain a better understanding of genetic testing and pregnancy, and what it will provide, watch the following video: