Discovering you’re pregnant should be one of the happiest times of your life. Aside from the nausea and exhaustion, you are thrilled to be bringing a new life into this world.
The process isn’t all sunshine and roses, though. As soon as your first prenatal visit, you are given the option of genetic screening tests to determine whether your unborn child is at risk for chromosomal abnormalities such as Trisomy 21 (Downs Syndrome), Trisomy 18 or Trisomy 13.
The misconception is that going through genetic screening is to determine whether or not there should be termination of the pregnancy. Genetic screening is 100-percent optional and the reason parents choose to go through with it is varied.
Some parents want to know if there is a risk to mentally prepare themselves for medical hardship. Others proceed with genetic testing (i.e. amniocentesis or chorionic villus sampling) for verification one way or the other.
This is noninvasive and poses zero risk to the fetus. It also carries the possibility of delivering a false positive, or bringing back a result of a chromosomal abnormality when there actually isn’t one. That is why parents are advised not to take action to terminate a pregnancy based upon a genetic screening result.
These procedures do produce a verified result because they sample cells that carry the same chromosomes as the fetus.
Amniocentesis: A long, thin needle is inserted into the mother’s abdomen to extract some of the amniotic fluid, which has the same genetic makeup as the fetus. It is typically done between the 15th and 20th week of the pregnancy. The procedure carries a 1 in 400 risk of miscarriage.
CVS: Depending upon where the placenta is located, a long tube is inserted either through the mother’s abdomen or the vagina to extract a small tissue sample from the placenta. This procedure is performed between 10–12 weeks, meaning a pregnancy termination would happen at a much earlier stage in fetal development than the amniocentesis. The one downside is that CVS cannot detect neural tube defects, such as spina bifida. CVS has a 1-percent risk of miscarriage, slightly higher than an amniocentesis.
If you have just learned you are pregnant – congratulations! You have either scheduled your very first prenatal exam or you are about to schedule it. This is what you can expect regarding your genetic screening schedule:
First-trimester screen: This is a blood test to measure hCG – the hormone used to detect pregnancy – and PAPPA, or Pregnancy-Associated Plasma Protein A. The optional piece of this screen is a nuchal translucency ultrasound, which measures the thickness of the back of the neck. It can detect Downs syndrome and other chromosomal abnormalities. This screen can be done independently of other tests, but that increases the risk of a false positive.
Maternal serum screen: The follow-up blood test after performing the nuchal translucency ultrasound increases the accuracy of the overall results. This is done between 15 and 20 weeks of pregnancy.
Dr. Andrea Greiner, a maternal and fetal medicine specialist at the University of Iowa Hospitals and Clinics, says screening is a good idea because “no one likes a surprise.”
“Knowing this information in advance can help expectant parents plan and prepare themselves as well as their home for a baby who may have special needs,” reads Livescience.
“Greiner said women need to ask themselves whether a positive diagnostic testing result would cause them anxiety if they choose to continue the pregnancy, or if these genetic findings may provide reassurance if they decide to terminate the pregnancy as a result of the diagnosis.”
Genetic screening is completely optional, so you should look at your own personality to determine what is best you. If you are an anxiety-driven person who would go crazy if your results come back positive, you may want to forgo the tests. If you think you can handle it, though, you may want to best prepare yourself.
“Most women do prenatal genetic testing to know what the risk is before the baby is born,” Greiner said. They would rather know the information during pregnancy than at birth to make plans or gain further knowledge.