Non-Invasive Prenatal Screening Methods

Throughout pregnancy there is a wish that is universally shared by all prospective parents –to learn that their baby is healthy. Along with the other tests and medical appointments to evaluate the pregnancy and the fetus’s health, growth and development, non-invasive prenatal testing (NIPT) has become a standard part of prenatal care in the past few years. NIPT is a blood test taken by a pregnant woman to check for genetic conditions of the fetus before birth. Despite its recent introduction, NIPT has been widely adopted by the medical community and is routinely requested by prospective parents in addition to traditional screening. Why was there a need for yet another screening test, and how does NIPT differ from the other screening tests that are already established in clinical practice?

To start with, let’s examine the term ‘screening tests’. A screening test lets the patient know if there is an increased risk of having the tested condition, and the results are provided in terms of possibilities or risk scores. Whereas, a diagnostic test —such as amniocentesis– provides a verdict on whether or not the patient has the condition tested. The results are definite; a diagnosis is made. Why then opt for a screening test instead of a diagnostic test? In the majority of cases, a screening test can be performed earlier during the pregnancy and is safer than a diagnostic test. As such, it is the ‘first step’ of the diagnostic journey, as only patients who are reported as ‘high risk’ on their screening tests would have to undergo invasive diagnostic tests.

The 1st and 2nd trimester screening tests currently in place include biochemical screening and ultrasound exams. These take place during weeks 11-13 of gestation and in weeks 15-20, and are the routinely established clinical tests to assess certain developmental milestones of the baby. The physician takes into account the fetus’s measurements, the pregnant woman’s hormonal levels and a set of variables such as age, weight or smoking factors to determine if there is an increased risk of the baby having one or more of the conditions tested. If the risk estimated is high, further testing in the form of diagnostic procedures –Chorionic Villus Sampling (CVS) or Amniocentesis– will be recommended by the physician to provide a definite diagnosis. Both of these are characterized as ‘invasive’, as they require inserting a needle through the abdomen into the placenta or the amniotic fluid to collect a sample. Critically, both carry a small risk of pregnancy loss so a lot of prospective parents struggle with the choice to continue with further testing.

The need for NIPT arises because the 1st and 2nd trimester traditional screening tests rely on statistical formulas that are not patient-specific. Consequently, a large number of patients end up having to unnecessarily undergo highly stressful and potentially dangerous procedures. Evidently, the basic principle of the ‘screening test’– to be able to test and accurately refer ‘high-risk’ patients for further testing – is not fully met by traditional measures. This leaves a crucial need for a more precise and sensitive screening method to be introduced in clinical practice to increase detection of genetic conditions. This need is addressed by the introduction of NIPTs.

With NIPT, genetic material (DNA) from the baby’s placenta, known as cell-free fetal DNA (cffDNA) can be extracted from the mother’s blood and examined. NIPT involves the use of specialized equipment and software, which analyze the baby’s DNA safely, accurately and affordably as early as the 10th week of pregnancy. Results are sent to the patients’ healthcare providers within a few working days. Thus, physicians and parents-to-be can learn earlier in the pregnancy if there is an increased possibility of the baby having a genetic disorder. If NIPT results are positive, the patient’s physician will recommend the next steps, taking other clinical findings also into consideration.

The role between traditional screening tests already established in clinical practice and NIPT is synergistic rather than antagonistic. Routine screening tests are routine for a reason –they work. However, the accuracy and sensitivity of traditional prenatal screening when it comes to detecting chromosomal abnormalities can be improved. NIPTs offer more accuracy and have the capacity to test for more conditions in this area, giving patients the information they need to know about the health of their baby. In traditional prenatal screening, age is the biggest factor when it comes to calculating a patient’s risk –the higher the patient’s age, the higher the risk is that the baby has a genetic condition. This reasoning is true for Down syndrome, one of the most common genetic disorders. However, age isn’t the only variable and a lot of younger pregnant women tend to go undiagnosed if they only undergo traditional prenatal screening. Moreover, there are a lot of conditions that are independent of maternal age that NIPT can screen for, such as microdeletions or single gene diseases. These conditions occur randomly and currently cannot be screened by traditional tests. It is therefore critical beneficial for all pregnant women to have an NIPT as it provides them with a lot of information they would not otherwise have had, had they only undergone standard prenatal screening.

NIPT is not just another screening test. NIPT gives parents the chance to know their baby without any risk to the pregnancy. NIPTs very high level of accuracy greatly improves prenatal screening. This means that even though pregnant women will still be referred for invasive procedures, those who do not need it will avoid the unnecessary risk exposure. The most important benefit NIPT offers to prospective parents is reassurance and time. Time that allows them to think, reflect and evaluate their choices; to gather all necessary information, decide on their future and manage their clinical care based on informed decisions.

Medical results should always be discussed with your healthcare providers.

For more information on what conditions our NIPT tests, VERACITY and VERAgene test for, please visit the tabs ‘VERACITY’ and ‘VERAgene’ on our website at www.nipd.com.