Genetic testing can be done prenatally or during pregnancy; it is offered to all women and is always optional. There are different types of testing, depending on the reason it should be done, based on a mother’s risk factors, age, past medical history, and family medical history. 

• Aneuploidy screening testing is optional. It tests for conditions in the fetus where there is an abnormal number of chromosomes. Most commonly it screens for conditions with an extra chromosome such as Trisomy-21 or Down syndrome. It also screens for Trisomy-13 and -18 which are conditions that are not compatible with life.  Conditions involving sex chromosomes such as Turner Syndrome (XO) or Klinefelter Syndrome (XXY) can also be screened.  These tests are never 100% accurate. They are non-invasive to the fetus, which is why they are typically the first line of testing. Screening can be done in several ways.

• First Trimester Screening (FTS) or Nuchal Translucency Ultrasound (NT):  Done between 11–13 weeks, this ultrasound looks for a nasal bone on the face and measures the nuchal fold. An increase in this measurement is associated with aneuploidies and possibly other defects.

• PAPP-A  Blood Test:  Can be used with the Nuchal Translucency to increase the accuracy of the diagnosis of aneuploidy. A low PAPP-A result is associated with Down syndrome.

• Non-invasive Prenatal Testing (NIPT) or Cell-Free DNA Blood Test:  Done as early as 10 weeks, this blood test will collect fetal cells from the placenta in the maternal serum. These cells can be grown and assessed for aneuploidy and also gender.

• Maternal Serum Alpha-Fetoprotein Blood Test (MSAFP):  Done between 15–18 weeks, this blood test can measure a protein made in the fetal liver that is passed through the placenta to the mother’s blood. It will assess for Down syndrome (low levels are seen) and neural tube defects (NTD) (high levels are seen). It is important to read the level in association with the appropriate gestational age. It is not as reliable as the other screening for aneuploidy and is used mostly for those who come for prenatal care after the first trimester. The anatomy screening ultrasound is done if an NTD is suspected.

• Anatomy Screen Ultrasound: Done between 18–22 weeks, this ultrasound looks at the anatomy of the baby. If any “soft markers” of aneuploidy are identified, diagnostic testing is offered: heart, kidney, brain, or limb defects.

• Refer women to a genetic counselor if:

  • Strong medical history for genetic conditions or birth defects

  • Strong family medical history of intellectual disability of unknown etiology

  • Positive carrier screening results

  • Positive screening test for genetic conditions

  • Fetal abnormalities are detected on an ultrasound

  • Women with a medical condition known or suspected to affect fetal development

  • Women who are considering invasive prenatal diagnostic testing

Ethical Considerations in Genetics:  Some may ask why a couple would choose not to have genetic testing. The answer is to ask: what do they want to do with the information they receive? Depending on the condition that is diagnosed, some may choose to terminate the pregnancy while others choose to continue with it. Genetic testing provides an opportunity for those who are continuing with the pregnancy the ability to prepare for how to raise a child with a particular genetic condition. Others may feel it would be too stressful to know, and they would not terminate the pregnancy, so they opt out of all testing. This is a personal decision and any choice made should be supported.