With the advent of new technology, pregnancy genetic testing has become more accessible and affordable. It helps expecting parents to identify potential fetal genetic abnormalities during pregnancy and their manifestation in the newborn. Prospective parents resort to genetic carrier screening to determine the risk of recessive disorders passing to the baby.
What is Pregnancy Genetic Testing?
Abnormal genes can lead to rare diseases, such as cystic fibrosis, sickle cell disease, Fragile X Syndrome, thalassemia, spinal muscular atrophy, some cancers, and Tay-Sachs disease. Pregnancy genetic testing helps you determine the vulnerability of a child to these inherited disorders. You will be aware if the passing of certain defective genes may trigger diseases in your child.
These disorders are recessive in nature and have a high chance of passing over the genetic defects of either parent or both to an offspring. Genetic carrier screening performed using blood tests help determine if you or your partner is carrying an abnormal gene that could cause an inherited disorder in your baby. No other prenatal test has the ability to determine such threats.
Genetic testing can be done during or before pregnancy to assess the risk. There is about 20% to 25% chance of a baby inheriting a recessive disorder when both parents have defective genes. If only one parent has a genetic disorder, the baby is likely to carry one defective gene along with a normal copy and doesn’t exhibit any symptoms. Carrying a defective gene does not mean the child has to suffer. The inherited disorder, even when passed by both parents to a baby, can be managed with proper care, preventing the suffering of the child.
What Are Recessive Disorders Pregnancy Genetic Testing Able To Identify?
Standard pregnancy genetic testing is able to identify over 400 disorders linked to flawed genes. Many of these disorders are extremely rare while some are manageable with treatments. The most common recessive disorders identified with carrier screening during or before pregnancy are:
- Cystic fibrosis that causes disorders impairing lungs and digestive tract.
- Sickle cell blood disorder
- Thalassemia blood disorder and related bone and liver issues
- Huntington’s disease
- Down syndrome
- Marfan syndrome
- Tay-Sachs disorder or lipid accumulation in nerves
- Canavan disease leading to nerve cell damage
- Familial dysautonomia or hyperinsulinism
- Gaucher disease
- Fragile X syndrome linked to retarded mental development
- Spinal muscular atrophy
- Tuberous sclerosis
- Niemann-Pick disease
- Roberts syndrome
- Lesch-Nyhan syndrome
- Color blindness
- Leber’s optic neuropathy
- Various cancers, such as hereditary nonpolyposis colorectal cancer
How Does Pregnancy Genetic Testing Work?
Genetic screening during or before pregnancy focuses on if your baby
- may develop a recessive disorder because of abnormal genes carried by parents
- is expected to inherit any recessive disorder
- is only a carrier but without risk of developing a genetic problem
Thus pregnancy genetic testing helps you know if your baby is at the risk of any genetic disorder because of genetic abnormalities in parents. When the result is analyzed in the light of maternal age, condition, parental ethnicity and health, and family history, it gives an idea about the potential odds of genetic disorders in your baby.
You can also identify triggers with genetic carrier screening and find out your chances of healthy pregnancy. Research studies show genetic testing has 85% success rate of identifying potential chances of recessive disorders in babies.
A positive result makes you aware and empowers you to take necessary steps based on diagnostic findings. You may meet a genetic counselor, plan to look after a child with special needs, reconsider your pregnancy, or make necessary lifestyle changes.
Who Needs Pregnancy Genetic Testing or Screening?
Parents are suggested to undergo pregnancy genetic testing or screening when
- The mother or father has a known genetic abnormality
- Either of the parents has a family history of a genetic disorder
- Ethnicity of a parent puts the baby at the risk of a genetic problem
- Any close relative of either parent is diagnosed with a genetic disease
- Earlier siblings have genetic disorders or birth defects
- Two or more miscarriages preceding the pregnancy
- Fetal physical abnormalities raising the risk of genetic disorder
- The mother is over 35 years or the father is much older
- Pregnancy complications indicate presence of multiple fetal physical abnormalities
Who is at Increased Risk of Genetic Disorders?
Ethnicity raises the risk of genetic disorders passing to a baby. It is discovered that Eastern European Jews and French Canadians are more prone to Tay-Sachs disease. Africans have a greater chance of inheriting sickle cell disease. Thalassemia passes from Mediterranean and Southeast Asian parents to their children. Pregnancy genetic testing confirms the risk of cystic fibrosis in European Caucasians.
The age of parents is another factor in promoting chromosomal problem and genetic mutation. Women becoming pregnant after 35 years requires carrier screening.
When Should I Go for Pregnancy Genetic Testing?
It can be performed during or before pregnancy. You can go for a genetic carrier screening before conceiving to assess the risk of recessive disorders when you have your baby.
You also have the option to undergo pregnancy genetic testing during the first trimester – between 10 and 12th weeks. It helps you find out if the child is likely to have triggers for genetic disorders.
The latest developments also make genetic screening tests possible in the second trimester. However, it is better to get the test done at the earliest.
How is Pregnancy Genetic Testing Done?
- The most common form of pregnancy genetic testing is a simple blood test. You may get reports in 2 to 6 weeks.
- Carrier screening involves identification of gene abnormalities in both parents.
- Genome product analysis helps examine genes to rule out a specific genetic disorder.
- Cell-free fetal DNA testing uses blood samples obtained during early pregnancy.
- Prenatal amniocentesis or testing of mother’s amniotic fluid between 15th and 20th week to identify chromosomal problems.
- Preimplantation genetic diagnosis performed on embryos prior to in vitro fertilization.
- A combined genetic screening test that includes blood test, amniocentesis, and placenta sample test.
Is There Any Risk of Side Effects on the Mother or Baby?
There is no known side effect of pregnancy genetic testing. Neither the mother nor the baby is affected by the screening. However, any positive result may cause emotional issues for parents as they may get stunned with the finding of unknown problems.
What are the Options for Parents Following Positive Findings?
Even when genetic testing of both parents yields positive results, the child has only a 20 to 25% of chances of being born with a recessive disorder. Parents may consult with a genetic counselor to find out ways to manage the problem and give their child a better life. You can plan elaborately in consultation with support groups on how to look after a child with special needs. With necessary lifestyle changes, you can also minimize triggers to a certain extent.
If you have carrier screening prior to conception showing positive findings, you may go for artificial insemination or in-vitro fertilization.
What are Advantages of Pregnancy Genetic Testing?
- Awareness about full range and severity of a possible genetic disorder is key to prevention and management. It makes you prepared to deal with the problem more effectively.
- Genetic testing during pregnancy allows you to know the risk of most noteworthy genetic disorders in your child and make informed decisions.
- The screening answers many unknown hereditary problems in your family. You may come to know about unknown problems linked to flawed genes.
- Your ability to identify your risk level facilitates adoption of lifestyle and alternative ways to manage symptoms and even go for treatments.
- Any woman can go for pregnancy genetic testing because it is without any side effects.
- When aware of a flawed gene in your partner, you may make a decision on pregnancy and go for adoption or in-vitro fertilization.
- It allows parents to prepare for child’s special needs, medical insurance coverage, treatment funding, child care, support groups and resources, and environmental effects.
- You may go for genetic engineering. The technology is fast evolving and helps to bypass many recessive diseases and illnesses.
- Recent research shows gene therapy is an effective way to treat many genetic disorders. If you are aware of the exact problem, you may plan for the treatment.
What are Cons of Pregnancy Genetic Testing?
Not all parents are strong enough to withstand the emotional effects of positive prenatal genetic screening. The sudden news of genetic abnormalities may cause psychological shock to prospective or expecting parents. They may be worried at the prospect of giving birth to a child with disorders while no assured treatment is available. The more worried a pregnant woman is, the more helpless she is to take care of herself.
The test results may become a source of family tension. Not all family members are ready to support your informed decision on pregnancy. As a result, you have to live in a stressful ambiance.
Pregnancy genetic testing or carrier screening may not be 100% accurate. There is about 5-10% chance of findings failing to predict the exact outcome. Genetic testing is not able to forecast the exact condition or severity of a recessive disorder in your baby. It will inform you only about the existence of gene abnormalities that may pass on to your child. You may come to know about a risk that may not severe enough to affect you, but cause stress during pregnancy.
Ravneet also blogs at www.wellnessguide.com
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