Prenatal Genetic Counseling
Every mother-to-be understands there are inherent risks in pregnancy and birth. Thankfully, most of the risks are minimal, and most babies are born completely healthy. Occasionally, the risk for a genetic disease or birth defect is a reality. In those cases, prenatal genetic counseling services at the Greenwood Genetic Center can help.
Prenatal genetic counseling is a field of genetics that focuses on caring for families with concerns about the health of their unborn baby. A prenatal genetic counselor can suggest the appropriate tests for correct diagnosis as well as offer education, resources and support.
Reasons for Prenatal Genetic Counseling Referral
Appointments for counseling are made by referral from a healthcare professional. In some cases, symptoms experienced during pregnancy will prompt an obstetrician to refer the patient to GGC for a genetic consultation. Another reason for referral is if one or both of the parents-to-be have a family history of genetic disorder and want genetic counseling before deciding to have children. Specific concerns are not limited to, but may include:
- Maternal age of 35 or older at delivery.
- Couples with a family history of genetic disorder.
- Positive prenatal screening test results.
- Couples from an ethnic background known to be at higher risk for genetic disorders (such as sickle cell anemia or Tay Sachs disease).
- Prenatal ultrasound findings.
- Personal history of two or more pregnancy losses.
- Family history of birth defects, a genetic disorder or intellectual disabilities.
- Couples who are blood relatives.
- Prenatal exposure to illegal drugs, alcohol, chemicals, infections or certain medications.
How to Prepare for Prenatal Genetic Counseling
The first thing to remember if you are referred for prenatal genetic counseling, is that a counseling appointment is only the first step in the process of confirming a diagnosis or detecting a complication. During your counseling session, your counselor will review your family, personal health and pregnancy history. He or she will explain any risks or conditions and help guide you through the testing process, if tests are offered.
At the Greenwood Genetic Center, our prenatal genetic counselors are health professionals with expertise in the field of prenatal medical genetics. They work closely with OB-GYNs and maternal fetal medicine specialists and, like all of our staff, genetic counselors and clinicians at GGC, are committed to patient care.
Follow these suggestions to help your counseling appointment go more smoothly:
- Bring a list of all prescription medications, supplements and medications you take.
- Be prepared to answer questions about your family’s health history.
- Family photos may help your counselor recognize patterns of genetic conditions in your family.
For more information about prenatal genetic counseling, please read our patient education brochures: Prenatal Genetic Counseling and Prenatal Screening and Testing.
Non-Invasive Prenatal Screening
What is Non-Invasive Prenatal Screening (NIPS)?`
NIPS is a screening test to determine if a pregnancy may be at an increased risk for a particular condition, so the family may decide if they would like
to pursue further testing during their pregnancy.
It looks at small pieces of chromosome material released by the placenta into the mother's blood stream. This test screens chromosomes 21, 18, 13, X and
Y for extra or missing copies. The most common conditions screened for are trisomy 21 (Down syndrome), trisomy 18, trisomy 13, Turner syndrome (monosomy
X), Klinefelter syndrome (XXY), and triple X syndrome.
This test will either come back with an increased risk for one of these conditions, or will come back with a decreased risk for all conditions screened
for, which is a risk of 1 in 10,000. This screening test can detect approximately 99.2% of cases of Down syndrome, and over 95% of cases of trisomy
18 and 13. However, it is just a screening test and cannot diagnose or rule out any of these conditions in a pregnancy.
How does NIPS differ from first trimester screening?
Both are screening tests that assess the risk for Down syndrome and trisomy 18 in pregnancy by looking at a sample of a mother's blood.
First trimester screening measures the levels of two proteins in the mother's blood (PAPP-A and hCG) and combines those results with a 12 week ultrasound to look at a measurement on the back of baby's neck called the nuchal translucency. Combining these numbers provides a risk for the pregnancy to have Down syndrome or trisomy 18.
NIPS looks at small pieces of chromosome material released by the placenta into the mother's blood stream. No ultrasound is included for the risk analysis. NIPS additionally screens for trisomy 13 and sex chromosome (X and Y) differences in a pregnancy, as well as fetal sex. NIPS is also more accurate at screening for Down syndrome and trisomy 18 than first trimester screening. However, a nuchal translucency scan (part of the first trimester screen) can detect other concerns such as an increased risk for a baby to have a heart defect.
It is important to remember both tests are just screening tests and neither can diagnose or rule out a condition in pregnancy.
What is the fetal fraction?
NIPS analyzes fetal DNA in the mother's blood. The amount of fetal DNA in the samples is known as the fetal fraction. NIPS is only accurate at or after 10 weeks gestation because this is when there is a high enough fetal fraction to do the analysis. If the test cannot detect enough fetal material, a non-reportable result will be issued. This is also known as a low fetal fraction. Non-reportable results and results with low fetal fractions (below 3%) have been associated with a higher risk for a chromosome condition in that pregnancy. Women with these results should consider meeting with a genetic counselor to discuss the option of further screening (like a level II ultrasound) or repeating their NIPS later in pregnancy?
What is the difference between a screening test and a diagnostic test?
A screening test (NIPS, first trimester screening, maternal serum screening) adjusts a woman's risk to have a pregnancy affected with a specific condition based on certain factors. The result will either increase or decrease the risk for those specific conditions.
A diagnostic test looks directly at the baby's genetic information to give a yes or no answer as to whether or not a baby is affected by a specific condition. A diagnostic test is the only way to know for sure whether or not a baby is affected during a pregnancy. However, starting with a screening test may help a woman decide if a diagnostic test during a pregnancy is necessary.
The NIPS test I had says it has a sensitivity and specificity of 99%. Does that mean my risk is 99% if my screening result is positive?
No. The sensitivity and specificity refer to the ability of the test to accurately call a negative result negative, or a positive result positive. If you're screening result is "positive" (remember, this is not a diagnosis), the risk is based on your age and the specific condition. This is because the risk for many of the conditions screened for by NIPS increases each year as a woman ages. So as a woman ages, it is more likely for a positive to be a true positive.
For example, a 21-year-old woman who has a "positive" NIPS for trisomy 13 actually has just a 6% risk that the pregnancy is actually affected. This is because trisomy 13 is a rare condition, NIPS is not as accurate for trisomy 13 as other conditions, and because of her age, her starting risk was very low.
A 35-year-old woman who has a "positive" NIPS for Down syndrome however, has a 79% chance that the condition is actually present, because her starting risk based on her age was higher, NIPS is most accurate at screening for Down syndrome, and Down syndrome is more common in the general population.
Can I have NIPS if I am pregnant with twins?
Yes! However, it is important to note if you have a fraternal twin pregnancy (where the babies each have their own placenta and amniotic sac) the results are less accurate than when used in screening a singleton pregnancy. This is because each twin's placenta may not release the same amount of chromosome material into the mother's bloodstream, leading to one twin being either underrepresented or overrepresented. Therefore, for twins, the risk is not reduced as much with a negative NIPS as it would be in a singleton pregnancy. However, NIPS is still the most accurate blood screening test we have for twin pregnancies for these conditions.
Does NIPS always accurately tell me the gender of my baby?
No! Fetal sex or gender, just like every other part of NIPS, is considered a screening test. While this is by far the most accurate part of NIPS, false results do occur. If you do receive an incorrect fetal sex prediction through NIPS, which is usually noticed at your 20 week ultrasound, do not panic. This does not necessarily mean anything is wrong with the baby. There are many reasons NIPS can predict the incorrect fetal sex or gender.
What is expanded NIPS?
Expanded NIPS refers to NIPS screening tests that look for abnormalities in chromosomes other than 21, 18, 13, X and Y.
The accuracy of looking for conditions beyond the standard panel drops significantly. However, it may be useful in a situation where there are differences on an ultrasound that are suggestive of a genetic condition and the mother declines diagnostic testing such as an amniocentesis.
One of the things an expanded NIPS test may look for are microdeletions or small missing pieces of chromosomes. Most of these conditions have a positive predictive value of less than 1%. This means that even if you tested "positive" for a microdeletion on NIPS, your risk may be less than 1% to actually have a child with that condition.
NIPS is a rapidly growing field. However, the accuracy of these new platforms is not yet well understood. Therefore, it is currently recommended that women interested in pursuing NIPS for screening early in pregnancy have the traditional NIPS panel.
Should I still consider having NIPS if I don't have a family history of Down syndrome?
Yes. In over 95% of cases of Down syndrome there is no family history of this condition. The same can be said for trisomy 13, trisomy 18, Turner syndrome, and Klinefelter syndrome. Therefore, not having a family history of one of these conditions does not decrease your risk for these conditions below your age related risk in pregnancy.
Similarly, having just one affected relative with one of these conditions does not significantly increase your risk, since that condition was likely new to that person in your family and not inherited. However, having two or more relatives with same chromosome condition may imply an increased risk for that condition.
Is there anyone who should not consider NIPS?
Yes. Women who have undergone an organ transplant are not good candidates for NIPS. This is because small pieces of the organ donor's DNA will be screened with the pieces of fetal DNA, giving an inaccurate result. Additionally, women who are currently affected with cancer should not undergo NIPS, since cancer cells often have chromosome differences that may lead to a false positive NIPS result. Finally, women on blood thinners such as Lovanox or Heparin are significantly more likely to have a non-reportable result, and should consider other screening options.
I heard my positive NIPS result may mean I have cancer? Is this true?
NIPS has detected a small number of cases of maternal cancer during pregnancy. However, these results look very different from a standard positive NIPS result. Often, these results come back positive for many chromosome conditions, giving both the laboratory and the genetic counselor an idea that something beyond the pregnancy may be going on. For example, these results will often say a baby has trisomy 18 AND monosomy 13, while the baby looks perfectly healthy on ultrasound. If you have had a positive NIPS result that turned out to be a false positive, you should not worry about an increased risk for cancer. Fortunately, most laboratories now can tell when an NIPS result is indicating the possibility of maternal cancer, and this would be discussed with you along with your results.
Is NIPS covered by my insurance?
Most insurance companies will cover NIPS for a woman of any age as it is the recommended test for all women interested in screening during pregnancy. However, some insurance companies deny all genetic screening and testing as an exclusion in their policy. If your testing is denied by insurance most NIPS companies will allow you to pay a reduced rate that can range from $100-$350 depending on the company. Ask your provider what company they use and what specific billing policy that company has to determine your exact price.
Is one NIPS company better than another?
Not necessarily. Most companies use very similar technologies for NIPS. Your genetic counselor or health care provider can help determine if one particular company is preferable based on your specific needs. However, for traditional NIPS most companies are equal in accuracy.