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Prenatal Genetics - Types, Indications, and Risks

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Prenatal testing, such as screening and diagnostic exams, can provide essential details about the unborn child's health.

Medically reviewed by

Dr. Kaushal Bhavsar

Published At June 9, 2023
Reviewed AtAugust 11, 2023

What Are Genetic Disorders?

Changes in a person's chromosomes or genes are the root cause of genetic disorders. A condition known as aneuploidy occurs when there is an extra or missing chromosome. There is an extra chromosome in a trisomy. In monosomy, a chromosome is absent. Mutations in genes are the root cause of inheritable diseases. Sickle cell disease, Tay-Sachs diseases, and cystic fibrosis are just a few examples of disorders that can be inherited.

What Is Prenatal Genetics?

Prenatal genetic testing informs parents of potential fetal genetic illnesses or birth defects. Unlike some common prenatal tests like blood tests or glucose screening, these tests are optional. Decide which tests are appropriate after speaking with the healthcare physician. In addition to regular pregnancy tests, some people obtain prenatal genetic testing.

Genetic testing during pregnancy is optional. Genetic illnesses are brought on by chromosomes or genes in a person. A gene is a component of the body's cells that stores instructions for how each system functions. The genes are stored on a chromosome. Congenital disorders are present before birth, and some of these conditions can be identified by medical professionals even before the baby is born.

What Are the Types of Prenatal Testing?

The two main types of prenatal testing are:

  • Screening Tests: Several birth defects, including genetic illnesses, can be detected during prenatal screening tests to determine if the child is more or less likely to have them. These examinations include a blood test, prenatal cell-free DNA screening, and ultrasound. The first or second trimester is typically when prenatal screening tests are available. Screening tests cannot provide a firm diagnosis. The doctor will confirm the diagnosis if the results show an elevated risk for a genetic condition.

  • Diagnostic Tests: Some diagnostic tests are techniques that can establish whether or not a developing infant has a chromosomal difference with greater than 99.9 % accuracy. Chorionic villus sampling (CVS) and amniocentesis are two different categories of diagnostic examinations. It is necessary to order diagnostic tests for particular genetic illnesses.

Between 10.5 and 13.5 weeks of pregnancy, CVS is performed. A tiny catheter is placed through the cervix, or a thin needle is put through the woman's belly to retrieve a small tissue sample from the placenta during the operation. Amniocentesis is done starting around week 15 of pregnancy. Amniocentesis involves taking a small sample of fluid from the amniotic sac, which is located around the growing baby, using a thin needle that is entered through the woman's abdomen. Depending on the test ordered, the cells obtained from either process may be utilized for chromosomal analysis or other genetic studies.

Chromosomal analysis findings typically take two weeks to arrive. However, depending on the ordered test, other genetic test results could take longer. The risk of miscarriage linked with diagnostic test methods is estimated to be up to 1% for CVS and less than 1% for amniocentesis.

Who Should Get Genetic Testing?

People frequently discover multiple cancer cases in their families. They are curious about its origin. Patients may ask their doctors for further information about their risks when getting a mammogram or colonoscopy.

Consider getting genetic testing if one has the following:

  • Recent or ongoing cancer diagnosis patients.

  • Many cancer types or multiple cancer patients in the family.

  • Abnormal results from a genetic test.

  • A personal or family history of genetic disorders.

  • Pregnant after 35 years of age.

  • Miscarriage or stillbirth history.

How Is Prenatal Genetic Testing Done?

The majority of prenatal genetic tests involve the pregnant woman's blood. The healthcare provider will do more intrusive tests to diagnose particular diseases if the screening test results show a high risk for a congenital condition. CVS and amniocentesis are examples of invasive diagnostic procedures.

Is It Necessary to Get Genetic Testing During Pregnancy?

No, genetic testing is not mandatory. The person makes a decision based on their own views or medical background. Some parents want to know if their child will be born with a condition to prepare for their child's care. Unfortunately, some families face heartbreaking findings and must decide whether to keep the pregnancy. The family and the doctor can decide whether to proceed with prenatal screening or diagnostic tests at any time.

What Screenings Are Done in the First Trimester?

First-trimester screening incorporates a pregnant woman's blood test and an ultrasound test. Both tests are typically carried out simultaneously between the 10th and 13th weeks of pregnancy. Two substances are measured by the blood test. A nuchal translucency screening ultrasound examination measures the space thickness at the back of the fetus's neck. The abnormal measurement indicates an increased risk of the fetus having Down syndrome (trisomy 21) or another type of aneuploidy. Additionally, it is associated with skeletal, heart, and abdominal wall defects.

What Screenings Are Done in the Second Trimester?

Second-trimester screening incorporates the accompanying tests. The levels of four different substances in the blood are measured using the "quad" or "quadruple" blood test. Down syndrome, Edwards syndrome (trisomy 18), and NTDs are all detected by the quad test. The test is done between 15 and 22 weeks of pregnancy. Between the 18th and 22nd weeks of pregnancy, major physical defects in the brain and spine, facial features, abdomen, heart, and limbs are examined by ultrasound.

Are There Any Risks for Genetic Testing During Pregnancy?

Prenatal exams are completely risk-free. A sample of blood is taken. The risk increases slightly if the person proceeds with diagnostic procedures like amniocentesis or CVS. These tests carry a risk of infection, bleeding, or miscarriage.


Prenatal testing is provided to pregnant mothers to determine whether there is a chance that the fetus will be born with a genetic disorder or birth defect. Prenatal testing may help select various pregnancy alternatives or unique management of the pregnancy and birth to improve the outlook for the baby.

Dr. Kaushal Bhavsar
Dr. Kaushal Bhavsar

Pulmonology (Asthma Doctors)


prenatal genetics
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