If you’ve decided to undergo prenatal genetic testing, you’re probably already aware of the huge range of testing options available to you at many different stages of your pregnancy. The prospect of choosing a test may seem a bit overwhelming, but we’ll break down the tests available, what to expect, and how to prepare for them during your pregnancy.
Initial Testing (Standard Prenatal Screening)
At your first prenatal visit, your doctor will begin the prenatal testing process by conducting a physical exam to assess your overall health. This will include checking your blood pressure, as well as a weight assessment. You’re also likely to be offered blood tests to check for sexually transmitted diseases, your immunity levels to diseases such as chickenpox and rubella, and you may also be offered a blood test for HIV. Other normal checks include regular urine samples to monitor glucose levels for signs of gestational diabetes, preeclampsia and other conditions that often affect pregnant women.
How to prepare: These tests are routine, and you’re likely to have had similar tests in the past. If you’re seeing a new health provider for this visit, it’s a good idea to make sure that they have access to your medical records. If you don’t have these (which is very common), you can call your general practitioner’s office and have your medical records sent over electronically. If your office is still using paper records, ask whether your provider can fax them.
Since urine samples are often needed, it may be a good idea to avoid going to the bathroom just before your appointment. If your doctor orders any additional tests, ask whether a period of fasting is required. You could also prepare by jotting down a list of questions you have for your doctor in advance, and keeping them at hand during the appointment.
Screening for Down Syndrome: The Nuchal Translucency Test
Beginning around week 10, you’ll be eligible to undergo non-invasive prenatal screening for genetic conditions. These tests assess your baby’s risk of inheriting a genetic disorder, and are an excellent option for mothers of advanced maternal age 35 or older at the time of birth, or those with any number of other risk factors for having a baby with a chromosomal abnormality.
A common option is the nuchal translucency screening, which requires only an ultrasound. Your physician will use the ultrasound image to assess whether the thickness of the baby’s nuchal fold (skin behind the neck) indicates a high likelihood of developing Down syndrome.
How to prepare: A full bladder may be required for your ultrasound, so don’t use the bathroom for a few hours before you arrive at your appointment. When you meet with your doctor, have a list of your questions ready in advance, so that you don’t forget anything you wanted to ask.
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Additional Prenatal Blood Tests for Genetic Disorders
While the nuchal translucency test only assesses risk for Down syndrome, other non-invasive prenatal blood tests can report on risk for Down syndrome plus a number of other conditions (including Edwards syndrome, Patau syndrome, and more).
How to prepare: Talk to your doctor about whether these tests are right for you. Your physician will need to order a genetic test, which you can then have performed at a lab near you. Prepare for your visit with your physician by writing down your questions and concerns in advance, and bringing them with you to the appointment. Make sure your physician’s office provides you all the information you need – including which lab you can go to, whether there are any special instructions (e.g. a fast required), and when you’ll get your results back. You can also visit the website of the test you and your doctor decide on – they’ll often have resources and information for patients like you.
After your results come in, you’ll meet with your physician again and perhaps also a genetic counsellor. Be ready to discuss your options. If the results of the tests indicate the risk of a birth defect, your doctor may recommend that you undergo more invasive testing (like chorionic villus sampling or amniocentesis) to provide more definitive insight on whether your baby has any genetic conditions.
Considering Genetic Counseling Options
The genetic screening process can be complicated to navigate aside from understanding your pregnancy, and you may benefit from genetic counseling services. Genetic counselors are experts who are trained to help patients decide which testing options are right for them, and to help them better understand the results of their tests. If results are positive for a genetic disorder, genetic counsellors can help by discussing the potential implications of the diagnosis, treatment optionspre, and next steps.