Finding out you’re pregnant can be an exciting and emotional time. Excitement, as well as questions and concerns about your baby’s health, are completely normal. Some couples may pursue prenatal genetic testing to help alleviate health concerns. 

“Prenatal genetic testing is a very personal and individualized decision,” says Sara Fisher, MS, CGC, Nebraska Medicine certified genetic counselor. “If you are concerned about your baby’s health, you should discuss the risks and benefits of prenatal testing with your health care provider to decide if genetic screening is right for you. If you think genetic testing may be something you are interested in, your provider or a genetic counselor can discuss testing options with you and how to understand the results.” 

Some families want to use test results for planning and preparation for current or future pregnancies. Test results that are low risk or negative may decrease concerns that the current pregnancy has a genetic condition or birth defect. While a positive or high-risk genetic test may prompt additional testing options during pregnancy or after birth. You may be referred to a specialist for additional discussion, detailed ultrasound, or other imaging like a fetal echocardiogram.  Each family may use the information from testing in different ways. 

There are three groups of prenatal test options: carrier, screening and diagnostic. 

Carrier screening tests are ideally performed preconception and can identify whether you, your partner, or both of you carry a gene mutation for certain genetic disorders such as cystic fibrosis or spinal muscular atrophy. If you or your partner have a family history of a genetic disorder, knowing that you are a carrier can allow for pregnancy planning including but not limited to the option of prenatal diagnosis, says Fisher.

A carrier screening test generally uses a blood sample from the arm. “If one partner is found to be a carrier of a certain condition, the other partner should also be offered screening as well to more accurately determine risk and to allow for appropriate genetic counseling,” notes Fisher. “Being a carrier does not mean your child will have a disorder. With conditions such as sickle cell, for example, when both partners are carriers of the same condition, then there is a 25% chance each child will have that diagnosis.”

The American College of Obstetricians and Gynecologists carrier screening guidelines recommend:

• Regardless of screening strategy and ethnicity, all patients who are pregnant or considering pregnancy should be offered carrier screening for cystic fibrosis and spinal muscular atrophy. They should also be offered a complete blood count and screening for thalassemia and hemoglobinopathies (inherited blood disorders). Fragile X premutation carrier screening (for intellectual disabilities) is recommended for women with a family history of fragile X-related disorders or intellectual disability suggestive of fragile X syndrome or women with a personal history of ovarian insufficiency. Additional screening also may be indicated based on family history or specific ethnicity.
• Couples with consanguinity (marriage with a common blood relationship) should be offered genetic counseling to discuss the increased risk of recessive conditions being expressed in their offspring and the limitations and benefits of carrier screening.

Screening tests are usually performed in the first or second trimester of pregnancy and are based on a pregnant patient’s preference. These tests can determine if a baby has a higher risk for conditions such as Down syndrome (extra copy of chromosome 21), Trisomy 13 (extra copy of chromosome 13), Trisomy 18 (an extra copy of chromosome 18) or neural tube defects like spina bifida. Some genetic conditions, such as Trisomy 18 or Trisomy 13, are more likely to result in a miscarriage and increase baby’s risk of being born with birth defects, developmental delays and other health issues. Other chromosome differences, like Klinefelter syndrome (XXY), may not have a high risk for major birth defects or miscarriage. 

There are several options for screening tests which may include blood tests, ultrasound or a combination of testing. The newest screening test for Down syndrome and some other chromosome differences is called cell-free fetal DNA or non-invasive prenatal testing/screening (NIPT/NIPS). This newest option is blood test which can be done as early as 10 weeks gestation with detection around 98.5% for the more common chromosome conditions. If any of these tests are positive, you may want to follow up with a diagnostic test to confirm their accuracy.

Diagnostic tests are the most accurate prenatal tests for chromosome differences and include: 

• Chorionic villus sampling (CVS), which takes a sampling from the placenta.
• Amniocentesis, which collects cells from the amniotic fluid around the baby.

“These tests are >99% accurate,” says Fisher. “However, since the CVS and amniocentesis tests carry a small risk of complications, many individuals may opt for screening initially.” Diagnostic testing can confirm or rule out chromosome differences in pregnancy and can also test for other, more rare genetic conditions associated with ultrasound findings or certain family history. 

Fisher says sharing genetic information can sometimes be difficult and emotional for parents. However, knowledge is power and can help prepare parents mentally and emotionally. “We want families to feel confident and fully informed about testing,” she says.  “We are here to support them through their entire pregnancy, no matter what the results may be.” 

Genetic prenatal testing can be performed before conception or during pregnancy. You may be more interested in pursuing genetic counseling before or after pregnancy if you:

• Want to review your and your partner's family history and screening options before pregnancy.
• Have a family history of intellectual disability, birth defects, genetic conditions, or chromosome abnormalities.
• Have prenatal screening results or an ultrasound that suggests an increased risk for birth defects or certain complications.
• Are considering chronic villus sampling or amniocentesis to test for genetic conditions.
• Are pregnant or plan to become pregnant at 35 or older.
• Have had multiple miscarriages or have a history of stillbirth or infant loss.
• Are of an ethnicity that may increase your risk for certain genetic disorders like sickle cell or Tay-Sachs disease. 
• Have been exposed to environmental factors, such as radiation, chemicals, drugs or infections that may pose a risk.
• Are cousins or close blood relatives with your partner.