Should I choose first trimester screening or Non-Invasive Prenatal Testing, and

[Anonymous]

Should I choose first trimester screening or Non-Invasive Prenatal Testing, and what can neither test detect?

[Genetic Counselor]

Both are valid options, and the right choice depends on cost, access, timing, and what you want to know.

• Non-Invasive Prenatal Testing This is the most accurate screening test for Down syndrome, Edwards syndrome, and Patau syndrome. It finds about 99 in every 100 babies with Down syndrome and gives far fewer false alarms than the combined test. It can be done from 10 weeks. It is more expensive, and sometimes returns a “no result”, which itself needs follow-up. The Society for Maternal-Fetal Medicine does not recommend routine screening for rare microdeletions with this test, because false alarms are more common. Screening for sex chromosome differences should be optional. Under Indian law, the baby’s sex is not disclosed.
• First trimester combined screening This is less expensive and widely available. It detects fewer affected babies and has more false alarms. Its big advantage is the nuchal translucency scan, which can pick up early signs of heart, skeletal, and other genetic conditions that blood tests alone cannot.

Guidelines advise choosing one screening approach rather than doing several and combining them. Even if you choose Non-Invasive Prenatal Testing, the 11 to 14 week scan is still valuable for checking the baby’s early structure, although the nuchal translucency measurement adds nothing extra for Down syndrome risk once Non-Invasive Prenatal Testing has been done.

Everyone needs to know that neither test can replace:
• Diagnose a condition Only chorionic villus sampling or amniocentesis can confirm a result.
• Check for single-gene conditions Beta-thalassemia, sickle cell disease, spinal muscular atrophy, and cystic fibrosis need carrier screening of the parents, ideally before or early in pregnancy.
• Replace the anatomy scan All pregnancies should have a detailed scan at 18 to 22 weeks.

Many people first see a doctor after 14 weeks. If you have missed the window for first trimester screening, second trimester blood screening or Non-Invasive Prenatal Testing are still available. A consultation with a clinical geneticist can help you decide which fits your pregnancy best.

[Author]

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