First Trimester Screening – Why Are So Many Tests Needed?

The first three months of pregnancy can feel exciting but also a bit overwhelming—especially when your obstetrician orders multiple tests and scans. The truth is simple: the first trimester is the most crucial phase for your baby’s development, and early screening helps detect problems before they become serious. Early screening helps catch issues at the earliest, safest, and most treatable stage.

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1. What exactly is first trimester screening?

It includes a combination of blood tests and an ultrasound (NT scan) done between 11–14 weeks to check the baby’s development and rule out genetic or chromosomal issues.

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2. Why do I need so many blood tests?

Each test gives different information:

• Blood counts → check for anemia & infections
• Thyroid test → important for baby’s brain development
• Sugar levels → detect early diabetes
• Urine test → check for infection
• Blood group & antibodies → prevent complications

They help identify issues early so treatment can start on time.

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3. What does the NT scan show?

The nuchal translucency (NT) scan measures the thickness at the back of the baby’s neck. It can indicate the risk of Down syndrome and other chromosomal abnormalities, and it also checks:

• Baby’s heartbeat
• Early structural development
• Presence of nasal bone
• Accurate dating of pregnancy

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4. Is the double marker test really necessary?

It’s optional but highly recommended. It combines your blood report with the NT scan to give a more accurate risk estimate for chromosomal problems.

It does not diagnose anything — it only tells us whether your risk is low or high.

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5. What if my screening test comes back high-risk?

Don’t panic. It only means you need further evaluation like NIPT, genetic counselling, or other diagnostic tests such as CVS or amniocentesis.

Most high-risk screening results still turn out normal after further testing.

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6. Are these tests safe for me and my baby?

Yes. All routine first trimester screening tests, including the NT scan and double marker test, are non-invasive and completely safe.

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7. Do I need to repeat these tests later in pregnancy?

Some tests, like blood sugars, hemoglobin, and thyroid, may need repeat checks.

But the NT scan and double marker test are done only once in the first trimester.

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8. When should I do these tests — what is the correct week?

Most first-trimester screening tests are done between 11–14 weeks.

• NT scan → 11–13+6 weeks
• Double marker test → 10–13+6 weeks

Other routine blood tests (thyroid, CBC, sugars, urine, blood group) can be done anytime in early pregnancy.

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9. What if I’m late and these weeks are already crossed?

If you miss the 11–14 week window:

• NT scan and double marker cannot be done later
• Your doctor may recommend second trimester screening (quadruple test) or NIPT depending on your gestational age

Don’t worry — we simply switch to the next safest option.

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10. Do all patients need the double marker or other marker tests?

It is recommended for all, but it becomes especially important for:

• Maternal age ≥ 35 years
• Previous baby with chromosomal disorder
• Family history of genetic problems
• IVF pregnancy
• Abnormal early scan findings
• Uncontrolled diabetes or thyroid disease
• Recurrent miscarriages

If you fall in any of these groups, the marker tests help give a clearer picture of the baby’s chromosomal risk.

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11. Can I skip any of these tests?

It’s better not to. These early tests help detect issues at the most treatable stage. Skipping them may delay diagnosis of conditions that could affect you or your baby.

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📍 Source: Dr. Shweta Mehta – DNB, Obstetrics & Gynaecology | United Multispeciality Hospital, Kandivali West, Mumbai.