Genetic Screening: 8 Frequently Asked Questions and Answers

By |2018-10-19T15:08:15+00:00June 18th, 2018|

Every parent wants to have a healthy baby.

While it’s not possible to guarantee a healthy baby, there are certain measures that can be taken to improve your chances.

Genetic screening is one of them. Genetic screening assesses the risk that a baby will be born with a certain birth defect or genetic disorder.

To address any questions or concerns you might have about genetic screening, we would like to answer some of the common questions that people have about it.

In this blog post, we’ll answer a few general questions about genetic screening…and then, we’ll get a bit more technical and tell you some things that it might help to know before undergoing genetic screening.

About Genetic Screening

1. Who should do genetic carrier screening?

Genetic carrier screening tests to see if you or your partner are carriers for specific genetic diseases that may have serious effects (developmental, cognitive or physical) on a child (i.e. Cystic Fibrosis, Spinal Muscular Atrophy etc).

Any patient can do genetic carrier screening (more on why you might want to do it below) but it’s especially relevant for patients who have a known genetic disorder, family history of a genetic disorder, or have a child with a genetic disorder. In fact, The American College of Obstetrics and Gynecology (ACOG) recommends that all patients who seek counseling prior to conceiving be offered genetic carrier screening before getting pregnant.

2. What happens if I am a carrier for a disease?

It depends on the type of inheritance the disease has. The majority of diseases tested for are Autosomal Recessive, which means that both partners need to be carriers in order to have an affected child with the disease.  In this case, if both partners are carriers, there is 25% chance that the pregnancy will result in a child with the disease.

If only one partner is a carrier for the disease, then there is a 0% chance that a pregnancy will result in an affected child. In the event that both partners are carriers – the option to proceed with IVF and Preimplantation Genetic Diagnosis (PGD) is available. This is a pre-pregnancy technology that identifies the embryos that are affected with the disease, preventing them from being transferred and thus significantly reducing the risk that a child will inherit a genetic disease. Depending on the results and the risks, some parents might decide to explore other avenues, like adoption or egg or sperm donation.

Additionally, if none of these options are acceptable to a couple, at the very least, knowledge is power. Knowing that your child is at risk of developing a certain disease can allow you to prepare as much as possible for every possible outcome.

3. Does genetic screening test for every genetic disease?

No. It’s not possible to detect every genetic condition, however there are expansive panels that can test for almost 200 different diseases! Additionally, there are many different genetic mutations that can lead to diseases that may not be known yet.

So keep in mind that, while negative test results are a good sign, they don’t guarantee that you will have a healthy baby. However, these genetic screening tests are quite expansive and detect the majority of commonly inherited genetic diseases.

Technical Questions

4. What causes genetic disorders?

Genetic disorders can be caused by problems with either chromosomes or genes.

So what exactly are chromosomes and genes?

A gene is what controls a person’s physical makeup or body process. A chromosome is the structure inside the cell that carries genes. Sperm and egg cells each have 23 chromosomes. During fertilization, when the egg and sperm join together, the two sets of chromosomes come together. So one half of a baby’s genes come from the baby’s mother and the other half come from the baby’s father.

When there are problems with either the chromosomes or genes, genetic disorders can result.

5. Is Preimplantation Genetic Screening (PGS) the same as Preimplantation Genetic Diagnosis (PGD)?

PGS also involves biopsying the embryo to assess the genetic makeup of the embryo, however it is only assessing that the correct number of chromosomes are present (i.e. 46XX or 46XY). PGD is specifically looking to see if the embryo is affected by the specific genetic disease you and your partner are carriers for. PGD can only be done for autosomal recessive disease where BOTH partners are carriers for the same disease or for autosomal dominant diseases where only ONE partner is a carrier.

6. What is autosomal dominant disorder?

Autosomal dominant disorders happen when only one parent is the carrier of a defective gene, in which case each child has a 50% chance of inheriting the disorder. If both parents happen to be carriers, then all children will be affected with the disorder.

7. What is autosomal recessive disorder?

On the other hand, autosomal recessive disorders happen only when both parents have the same defective genes. In order to be affected, a child needs to have TWO copies of the abnormal gene, which will then result in the disorder. So for couples who are both carriers for the SAME autosomal recessive disease, they have a 25% chance of having a child affected with the disease.

8. What is a carrier?

A carrier is a person who has inherited a variant form of a gene (in autosomal recessive disorders they don’t have any symptoms of the disease). They carry one copy of a gene that works correctly and one that works incorrectly.

If just one parent is a carrier of a disorder, there is a 50% chance that the child will be a carrier of the disorder too. If both parents are carriers of an abnormal gene, there is a 50% chance that the child will be a carrier of the disorder and a 25% chance that the child will inherit the disorder.

Summing Up

We hope that the information in this blog post gives you a better understanding of genetic screening and how it can help you improve your chances of having a healthy baby, as well as guide your future decision-making.

If you would like to find out more about genetic screening, feel free to schedule a new patient consultation with us or give us a call at (949) 706-2229. We’re here to answer any questions you have!