September 3, 2020

Advances in Pregnancy Care: What Parents Need to Know About Genetic Screening

By Shivani Chinnappan, SWHR Programs Coordinator

In 2020, SWHR is bringing attention to the need for advances in diagnostic and screening tests across a variety of diseases and conditions to improve the health of women. In this blog, we talk about options for prenatal and early carrier genetic screening.

In considering a future pregnancy, immediate concerns for parents-to-be are how to prepare for a healthy pregnancy and how to set their child up for success early in life.

Noninvasive prenatal screening (NIPS) and expanded carrier screening (ECS), both forms of genetic screening, allow families to gain insight into the risk posed by certain heritable conditions. Below, SWHR profiles both types of screening and discusses what families should know before talking to their clinician.

Noninvasive Prenatal Screening

After an individual becomes pregnant, there are methods for screening the developing fetus for risk of heritable disorders. Noninvasive prenatal screening (NIPS) uses a blood sample, taken from the birthing parent, to examine cell-free DNA (cfDNA) from the fetus that is also found in the parent’s bloodstream. The test poses no risk to the parent or fetus. NIPS can tell parents whether their child has an increased risk for certain genetic conditions, but results cannot provide definitive diagnoses.

First introduced in 2011, NIPS is most commonly used to screen for chromosomal conditions such as Down syndrome; however, it is also capable of detecting an increased chance for a number of single-gene disorders, fetal sex, and some autosomal-recessive and X-linked genetic conditions.

Although amniocentesis and chorionic villus sampling (CVS) are the gold standard for fetal diagnosis, both pose a potential risk to the pregnant parent and the fetus. As such, NIPS has grown in popularity as it is highly sensitive in screening for disease risk as early as 10 weeks into the pregnancy. Following positive results from NIPS, amniocentesis or CVS can then be performed to confirm a potential diagnosis.

Clinically, recent guidance from the American College of Obstetricians and Gynecologists (ACOG) indicates that prenatal screening, including cfDNA-based noninvasive tests, should be offered to all pregnant persons. ACOG specifically states that cfDNA noninvasive prenatal tests offer superior sensitivity and specificity compared to maternal serum screening.

Not all parents choose to know whether their child may be at an increased risk for a heritable genetic condition, and positive NIPS results may cause unnecessary anxiety through the remainder of the pregnancy should the child ultimately be born without the condition in question. However, for families who do want additional information, it can be helpful to consider a possible diagnosis in advance to better prepare for the birth of a child with special needs.

Expanded Carrier Screening

Carrier screening is a type of genetic screening to determine carrier status for recessive and X-linked genetic conditions. If both the parents carry genes for heritable conditions, there is a risk of passing that condition on to their future children — even if both parents are healthy. In some cases, only the pregnant parent needs to be a carrier for their child to be at increased risk for the genetic condition.

Carrier screening is typically conducted using a blood or saliva sample. It is ideally performed before pregnancy to ensure couples are aware of risk prior to conception. The panel of conditions tested will vary depending on the testing provider, but there are sets of common heritable conditions that are recommended by ACOG. As some heritable conditions occur more commonly in specific demographic groups, doctors may recommend individuals from those groups receive additional tests.

For couples who are interested in additional screening, a process called expanded carrier screening (ECS) tests for a wider panel of conditions than traditional carrier screening. While family medical history is often used to guide screening decisions, for many diseases or conditions, there’s often no family history, making ECS potentially useful to catch genetic risks that may not otherwise be apparent in a family tree.

ECS may also be an option for individuals who are uncertain about their genetic background. One in 10 individuals self-report an ethnicity inconsistent with their background, which may inadvertently lead doctors to recommend screening tests that are not a match for patient needs. ECS can offer patients a more thorough alternative to traditional testing.

On the other hand, wide-range testing may cause increased anxiety. In a 2019 NPR interview, Aleks Rajkovic, chief genomic officer at the University of California, San Francisco, suggests that not all families will require ECS. “Some panels are testing for very rare disorders that have only been seen in a single family, so the likelihood of a client ever actually having the variation is infinitely small,” he said. He suggested that families consult a professional to gain insight on their chances of carrying certain rare disorders before deciding whether ECS is right for them.

Clinical recommendations on ECS remain somewhat unclear. ACOG guidelines currently leave the decision on carrier screening to be made at the discretion of the patient and their health care provider. There exists a general lack of consensus in the clinical community as to who should be offered ECS and how to determine which conditions should be included in expanded and targeted screening panels.

What Parents Need to Know

If possible, parents and future parents should ask their clinicians questions about genetic screening prior to becoming pregnant. Talk to your clinician about your ethnic background and family history of disease, especially if you are not sure about your ancestry or if you do not have a complete family medical history. Make sure to ask about the risks and benefits of each type of screening test you are offered as well as whether or not it is covered by your insurance.

The decision to pursue genetic screening should ultimately be made by the parents in collaboration with their health care providers. Providers must carefully consider how to counsel parents-to-be regarding possible positive screening results. Poor understanding of screening results may lead to increased anxiety and inaccurate assumptions about risk. However, used wisely, genetic screening options may provide parents with improved knowledge to inform them in their journey to starting a family.

For more information on genetic screening, check out SWHR’s interview with a genetic counselor. Learn more about innovative new methods of screening and diagnosis for diseases and conditions affecting women.

SWHR’s genetic screening and diagnostic testing blog series is supported by a grant from Myriad Women’s Health. SWHR maintains editorial control and independence over blog content.