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Pregnancy is a journey filled with excitement, anticipation, and, let's face it, a fair share of anxiety. As expectant mothers, we're often faced with numerous decisions, and one of the more significant ones involves prenatal testing.
As OB-GYN and women's health expert, Dr. Caledonia Buckheit, explains: "When it comes to genetic testing, there are screening tests (like the quad screen or cell free DNA) that tell you the likelihood that your pregnancy is affected by a genetic condition, and there are diagnostic tests, which tell you if your pregnancy is affected with a condition, yes or no. That's where amniocentesis and CVS come in."
Two common procedures that often come up in discussions with healthcare providers are amniocentesis and chorionic villus sampling (CVS). But what exactly are these tests, and how do you decide which one, if any, is right for you?
Both amniocentesis and CVS are diagnostic tests that can provide valuable information about your baby's genetic health. However, they each have their own set of pros and cons, and the decision to undergo either test is deeply personal. Let's dive into the details of these procedures to help you make an informed choice.
What are amniocentesis and CVS?
Amniocentesis is a procedure typically performed between 15 and 20 weeks of pregnancy. During this test, a thin needle is inserted through the abdomen to collect a small amount of amniotic fluid surrounding the baby. This fluid contains cells shed by the fetus, which can be analyzed for genetic disorders, like Down syndrome or trisomy 13.
CVS, on the other hand, is usually done earlier in pregnancy, between 10 and 13 weeks. In this procedure, a small sample of cells is taken from the placenta. These cells, which come from the same source as the fetus, can also be tested for genetic abnormalities and chromosomal conditions, like Down syndrome or trisomy 13.
Are CVS and amniocentesis test results accurate?
Yes, CVS and amniocentesis are highly accurate tests that check your baby's chromosomes. While they can't detect every genetic condition, they can spot specific ones — especially if they run in your family or there’s a higher risk.
Sometimes CVS results (about 1-2% of cases) show mixed cell patterns called mosaicism. When this happens, doctors typically recommend an amniocentesis to double-check the results and get the clearest possible picture of your baby's health.
Both tests are powerful tools in your pregnancy journey, helping you make informed choices with your healthcare team. Your doctor can help you understand which option might work best for you.
Is CVS better than amniocentesis?
The answer to this question isn't straightforward, as both tests have their advantages. CVS can be performed earlier in pregnancy, which means you can get results sooner. This can be particularly beneficial if you're considering terminating the pregnancy in case of severe genetic abnormalities. However, amniocentesis can detect certain conditions that CVS can’t, like neural tube defects.
Why do doctors recommend amniocentesis?
Doctors may recommend amniocentesis for several reasons. It's often suggested for women over 35, as they have a higher risk of having a baby with chromosomal abnormalities. Other reasons include abnormal results from earlier screening tests, a family history of genetic disorders, or a previous pregnancy affected by a chromosomal abnormality.
Amniocentesis can detect a wide range of genetic disorders, including Down syndrome, cystic fibrosis, and some structural problems, like spina bifida. It's also the most accurate prenatal test available, with a detection rate of over 99% for Down syndrome.
When there's too much amniotic fluid around your baby (called polyhydramnios), doctors can also use amniocentesis to drain the extra fluid, helping restore comfort and balance for both you and your growing baby.
What is the biggest drawback to amniocentesis?
The primary concern with amniocentesis is the small risk of miscarriage associated with the procedure, which is low, but not zero. According to recent studies, the risk is estimated to be increased by about 0.5%. This is significantly lower than previously thought, thanks to improvements in ultrasound technology and procedure techniques.
However, it's crucial to remember that this risk is in addition to the background risk of miscarriage that exists in any pregnancy. The decision to undergo amniocentesis should involve careful consideration of the potential benefits and risks.
Why do doctors recommend CVS?
Healthcare providers typically recommend this test when there's a higher chance of genetic differences, which could happen for several reasons. Similar to amniocentesis, some common situations include being 35 or older during pregnancy, having certain results on initial screening tests, or when genetic conditions run in the family.
The procedure involves collecting a tiny sample from the placenta through the cervix or through the abdominal wall with a needle (like amniocentesis), which lets doctors check your baby's chromosomes. Unlike some other prenatal tests that just estimate possibilities, CVS can provide clear answers about specific genetic conditions. Plus, you can get results earlier than with other diagnostic tests like amniocentesis, which helps you and your healthcare team plan ahead.
It's worth noting that CVS isn't recommended for everyone — it's specifically offered to those who might benefit most from the information it provides. While the test is generally safe, there is a small risk of pregnancy loss that your doctor will discuss with you. Together with your healthcare team, you can weigh the benefits and risks to make the choice that feels right for your situation. Remember, every pregnancy journey is unique, and there's no one-size-fits-all answer when it comes to prenatal testing.
How risky is CVS to the fetus?
Like amniocentesis, CVS also carries a small risk of miscarriage. The risk is slightly higher than that of amniocentesis, estimated at about 1 in 300, or 0.29%. However, this risk has also decreased over time with improved techniques.
CVS has an additional, rare risk of causing limb defects in the baby if performed before 10 weeks of pregnancy. This is why the procedure is typically not done earlier than 10 weeks.
Why would a woman choose not to have a procedure such as amniocentesis or CVS?
Despite the valuable information these tests can provide, some women choose to forgo them. There are several reasons for this decision:
- The risk of miscarriage, although small, is a concern for many women.
- Some women feel that the information wouldn't change their decision to continue the pregnancy, regardless of the results. "But," as Dr. Buckheit suggests, "keep in mind, the information learned could help you plan and prepare for a baby with genetic differences."
- The procedures can be uncomfortable or anxiety-inducing for some women.
- Religious or personal beliefs may influence the decision.
- Some women prefer to rely on non-invasive prenatal testing (NIPT), which can provide a good deal of information about certain genetic conditions through a simple blood test.
It's important to remember that there's no right or wrong decision. What matters is making the choice that feels right for you and your family.
Making your decision
Deciding whether to undergo amniocentesis, CVS, or neither is a deeply personal choice. It's essential to have open discussions with your healthcare provider and your partner, if applicable. Consider your personal beliefs, your ability to cope with potential results, and how the information would impact your pregnancy decisions.
Remember, these tests are optional. You have the right to decline any prenatal testing if you feel it's not right for you. Your healthcare provider is there to provide information and support, not to make the decision for you.
Pregnancy is a unique journey for every woman, and what works for one may not work for another. Trust your instincts, arm yourself with information, and make the choice that feels right for you and your baby. After all, you know your situation best, and you're already making important decisions for your little one's well-being.
Tassia O'Callaghan is an experienced content writer and strategist, having written about a vast range of topics from chemical regulations to parenting, for brands like Peanut App Ltd, Scary Mommy, Tally Workspace, and Office Christmas. She's an advocate for realistic sustainable living, supporting small businesses (author of A-Z of Marketing for Small Businesses), and equity across all walks of life. Follow her on LinkedIn or TikTok, or see more of her work on Authory or her website.
