Each of our pregnant families is offered prenatal screening for Cystic Fibrosis (CF), trisomies (i.e. Downs Syndrome and Trisomy 18), and open neural tube defects (ONTD). The discussion surrounding these available prenatal screens will occur during your first several visits with us. Whether or not to pursue prenatal screening during your pregnancy is a personal decision requiring an individualized approach.
The prenatal screens listed below are not meant to be diagnostic of trisomies, CF, or ONTD, but are highly sensitive in detecting high risk pregnancies that may warrant further testing (i.e. amniocentesis).
Non-invasive DNA prenatal testing (NIPT)
Non-invasive DNA prenatal testing (NIPT) is a highly accurate blood test taken from the pregnant mother any time after 10 weeks gestation. During pregnancy, DNA from the baby crosses into the mother’s bloodstream. Specialized laboratories look at this DNA for evidence of more common chromosomal abnormalities such as Down Syndrome, Trisomy 18, Trisomy 13, certain sex chromosome abnormalities and Triploidy. Detection rates for these conditions can be as high as >99% with a very low false positive rate of <1 %. It is important to know that not all insurance companies will cover the cost of this test and due to some high out-of-pocket deductibles, we would encourage you to contact the laboratory we use to learn what your out-of-pocket cost may be.
Sequential Screen is a two-part screen initiated between 11-14 weeks In the first trimester, a combination of a high-level ultrasound to measure the thickness of your baby’s neck fold and a maternal blood test measuring particular proteins and hormones will be obtained. This first part of the screen detects increased risk for Down Syndrome and Trisomy 18. If no abnormalities are yet detected with the first trimester screen, we will collect another maternal blood sample between 16-18 weeks. This blood test will provide additional risk assessment for Down Syndrome, Trisomy 18, and open neural tube defects (ONTD). Detection rates when both the first and second trimester samples are collected are 90% for Down Syndrome and Trisomy 18 and 80% for ONTD. The false positive rate with this screen is 3.7%. Insurance companies may be more willing to cover this screening over NIPT due to lower cost.
Maternal Serum AFP
Maternal Serum AFP is a blood test drawn between 16-18 weeks gestation which shows if you are at increased risk of having a baby with open neural tube defects (ONTD). Your baby’s neural tube will eventually develop into the baby’s brain and spinal cord. An abnormality in this structure can lead to paralysis and other physical and/or mental problems. The detection rate of ONTD is 80% with a 5% false positive rate. Of note: This screening is already included when choosing the sequential screen.
Cystic Fibrosis Carrier Screening
Cystic Fibrosis Carrier Screening is a screening blood test for couples to find those who have a higher risk of having a baby with an inherited condition called Cystic Fibrosis (CF). To have a baby with CF, a baby must inherit two CF genes, one from each parent. A person will not be symptomatic if they are only a “carrier” of a CF gene. If only one parent carries the CF gene, the baby cannot have CF. Up to one in every 2,500 babies are born with CF and the risk is greater when there is a known family history of CF or carrying of a CF gene. If you choose to do this screen, we will obtain a blood sample from the mother for CF mutation screening. If a mutation is detected, then we will need to obtain a blood sample from the other biological parent. Because this screen cannot test for all CF mutations, there is a small chance your baby may be born with this condition despite a “screen negative” finding.
Fetal Survey Ultrasound
Fetal survey ultrasound is performed between 18-20 weeksgestation. This abdominal ultrasound looks to assess your baby’s anatomy such as the heart, spine, kidneys, lungs, extremities, face, brain, genitalia, gastrointestinal system, as well as the placenta. Sometimes views are limited and you will be asked to return at a later date for additional views. At this ultrasound, you may choose to learn the gender of your baby if the baby’s position allows.
The information prenatal screening can offer may be more important to some expectant parents than to others, and many of our clients will opt out of some or even all screens. Reasons for this are individual but may include:
They have no known risk factors (i.e. family history of chromosomal abnormalities or neural tube defects, maternal age is under 35 years old, no history of diabetes, no family history of genetic disorders). It is important to remember, however, many infants affected by neural tube defects or chromosomal abnormalities have no known risk factors.
- Identifying these fetal problems ahead of time will not change how they proceed with the pregnancy.
- They want to avoid the anxiety they may experience while waiting for screen results.
- They want to avoid unnecessary worry and testing that may follow a false-positive result.
- They have a personal belief or value system to trust in the well-being of their baby without the need for prenatal screening.
- The cost of the screen is not covered by insurance.
If you have any further questions regarding prenatal screening, feel free to contact us or initiate discussion during one of your prenatal visits.