Testing the Genetic Code in Carrier Screening

By: Dr. Angie Beltsos, Medical Director & CEO

carrier screeningPreconception counseling is developing into something larger than life. We, as doctors talking to patients before they are pregnant, continue to strive for simplicity and comprehensiveness.

One egg and one sperm create a new person with genetic codes about who we are and who we will become. Human features are in genetic recipes that come half from the egg and half from the sperm. There can be mistakes in the code that get passed on to the child and in recessive traits, as long one normal part gets passed on, the abnormal one may be overshadowed. In order for the abnormality to show itself, both the egg and sperm would have to contribute the abnormal gene. Many conditions or diseases are passed on to children through generations and a simple but important blood test can detect these genetic diseases. All women who want to have a baby should consider the testing of their genetic code called “carrier screening.” Up to half of pregnancies are unplanned! Therefore testing, when going in for pap smears or birth control pills, is also a consideration. At our clinics, we offer carrier screening to couples trying to conceive which may help to identify abnormalities and optimize the chance of having a healthy baby.

Now, the American College of OB/GYN (ACOG) recommends that screening be offered to all women for these conditions… and not just depending on their ethnic background. Studies show that most people in the US do not know their ethnic background and therefore asking that does not help decipher who is at risk. Earlier this year the ACOG has announced it recommends offering additional carrier screening to all women, regardless of ethnicity or family history. The two new Committee Opinions are published in March 2017 of Obstetrics and Gynecology. Read more here.

In the past, specific ethnicity was the basis for the testing and now these two new Committee Opinions go beyond previous thoughts to broaden who should be tested and for what. The new opinions recommend that the doctor have a standard approach ethnic-specific, pan-ethnic or expanded carrier screening. It used to be that just Cystic Fibrosis (a condition that can make it hard to breathe and affects the lung as well as the gut at times) be offered to all patients. Now the recommendation includes screening for Spinal Muscular Atrophy and a complete blood count for hemoglobinopathy like thalassemias. Dr. Joseph Biggio, Director of Maternal Fetal Medicine at the University of Alabama Birmingham and author of the Committee Opinion states, “A growing number of Americans are also of mixed or uncertain ethnic backgrounds, which means we may not identify some people who are at risk of passing genetic conditions to their children when we follow ethnic-based recommendations.” The updated standards also discuss expanded carrier screening which tests for up to several hundred conditions simultaneously!

Therefore, whether she is on the pill and someday might want to have a baby, or if she and her partner are trying to get pregnant, make sure to offer this testing. It is very important for her to know if she carries any recessive traits. In the event that both carry the same genetic mutation, there is typically a 25% chance the baby could inherit it. If she and her reproductive partner both do, there is a way to help avoid having a baby with the severe form of that condition. To avoid this, one option is to consider In Vitro Fertilization (IVF) with Preimplantation Genetic Diagnosis (PGD). Couples can screen out abnormalities like Cystic Fibrosis, SMA or Thalassemia by identifying which embryos are affected. Without testing, many couples find out that they carry the disease because the baby is born with this. Unfortunately, some of these conditions result in not surviving into adulthood. Of course, antenatal testing as well as newborn screening also are important time points to also check the baby.

Based also on family history and personal values, the health care team as well as genetic counselors can counsel women and their reproductive partners about their options. Furthermore, if someone tests positive for a disease, their family members should be aware so that they might also tested, as they are at risk for carrying the condition as well.

The advent of genetic testing is transforming the medical world. DNA testing identifies who is at risk for certain problems, what medicine is best for high blood pressure, which chemotherapy is best for treating cancer. Each person is unique. Understanding our DNA may allow for clarity but also may create Pandora’s Box of information overload. We will see much more DNA testing in medicine to come so, fasten your seatbelt. In the meantime, have carrier screening performed to be proactive and take charge of future children’s health.

“Natural forces within us are the true healers of disease.” – Hippocrates