Fetal Biochemical Screening

Fetal Biochemical Screening

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Overview

Fetal biochemical screening is a non-invasive method used to estimate the risk of chromosomal abnormalities, including Trisomy 21 (Down syndrome), Trisomy 18, and Trisomy 13. It involves analyzing specific biochemical markers in maternal blood during pregnancy. This screening does not diagnose a condition but identifies those pregnancies at higher risk who may benefit from further diagnostic testing such as CVS or amniocentesis.

First Trimester Screening (11–13+6 weeks)

First trimester screening combines maternal serum markers — free β-hCG and PAPP-A — with nuchal translucency (NT) measurement via ultrasound. This integrated result estimates the risk for Trisomy 21 and 18. The presence of nasal bone, ductus venosus Doppler, and tricuspid valve flow may also be incorporated to improve screening accuracy.

Second Trimester Quadruple Screening (15–22 weeks)

The quadruple test includes four serum markers: Alpha-fetoprotein (AFP), total hCG, unconjugated estriol (uE3), and inhibin-A. It assesses the risk of Trisomy 21, Trisomy 18, and neural tube defects. It is most accurate between 16–18 weeks but can be performed up to 22 weeks gestation.

Cell-Free DNA Screening (cfDNA / NIPT)

Cell-free fetal DNA testing, also known as Non-Invasive Prenatal Testing (NIPT), analyzes fetal DNA fragments circulating in maternal blood. It provides a highly accurate screening for common trisomies (21, 18, 13), sex chromosome aneuploidies, and selected microdeletions. It can be performed from 10 weeks onwards and is especially useful in high-risk pregnancies.

Interpretation and Follow-up

A positive biochemical screening result indicates increased risk and should be followed by confirmatory diagnostic tests such as chorionic villus sampling (CVS) or amniocentesis. The final interpretation should always consider maternal age, gestational age, ultrasound findings, and previous pregnancy history.

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Note: Select English or Hindi; answer accordingly. / अंग्रेजी या हिंदी चुनें; उसी में उत्तर दें।

1. Which maternal serum marker is increased in open neural tube defects? 1. खुले न्यूरल ट्यूब दोषों में कौन‑सा मातृ सीरम मार्कर बढ़ा हुआ होता है?
A. Alpha‑fetoprotein (AFP)
B. Low hCG
C. Low AFP
D. High inhibin‑A only

2. The combined first‑trimester screening includes nuchal translucency and which biochemical markers? 2. संयुक्त प्रथम तिमाही स्क्रीनिंग में नचाल पारदर्शिता और कौन‑से बायोकेमिकल मार्कर शामिल होते हैं?
A. Free β‑hCG and pregnancy‑associated plasma protein‑A (PAPP‑A)
B. AFP only
C. Inhibin‑A only
D. Maternal glucose

3. In the second‑trimester quad screen, which pattern is typical for Down syndrome (Trisomy 21)? 3. द्वितीय तिमाही क्वाड स्क्रीन में डाउन सिंड्रोम (ट्राइसोमी 21) के लिए किस पैटर्न की आमतौर पर सूचना मिलती है?
A. Low AFP, high hCG, low uE3, high inhibin‑A
B. High AFP, low hCG, high uE3, low inhibin‑A
C. All markers normal
D. Only AFP elevated

4. Cell‑free fetal DNA (cfDNA / NIPT) is best described as: 4. सेल‑फ्री भ्रूणीय DNA (cfDNA / NIPT) को सबसे अच्छा कैसे वर्णित किया जाता है?
A. A high‑sensitivity noninvasive screening test analyzing fetal DNA fragments in maternal plasma
B. A diagnostic invasive test equivalent to amniocentesis
C. A test that measures maternal antibodies only
D. A fetal ultrasound parameter

5. Which factor does NOT affect maternal serum marker MoM (multiples of the median)? 5. कौन‑सा कारक मातृ सीरम मार्कर MoM को प्रभावित नहीं करता?
A. Maternal weight
B. Gestational age at sampling
C. Maternal ethnicity
D. Paternal eye color

6. A high maternal serum AFP with a normal fetal anatomy scan suggests which next step? 6. सामान्य भ्रूणीय एनाटॉमी स्कैन के साथ उच्च मातृ सीरम AFP किस अगले कदम का सुझाव देता है?
A. Repeat dating/confirm gestation, evaluate for multiple pregnancy, consider targeted anatomic reassessment and neural tube defect evaluation
B. Immediate chemotherapy
C. Ignore result
D. Only maternal glucose test

7. Which statement about screening vs diagnostic tests is correct? 7. स्क्रीनिंग बनाम डायग्नोस्टिक परीक्षणों के बारे में कौन‑सा कथन सही है?
A. Screening estimates risk and may require confirmatory diagnostic testing (CVS/amniocentesis) if positive
B. Screening provides a definitive genetic diagnosis
C. Diagnostic tests are always noninvasive
D. No screening is ever useful

8. Integrated screening combines first‑trimester and second‑trimester markers. Its advantage is: 8. एकीकृत स्क्रीनिंग पहले‑तिमाही और दूसरे‑तिमाही मार्करों को मिलाती है। इसका लाभ क्या है?
A. Higher detection rate for trisomies compared with either test alone
B. Instant diagnostic result
C. Eliminates need for ultrasound
D. Always cheaper than single tests

9. A positive cfDNA/NIPT result should be followed by: 9. सकारात्मक cfDNA/NIPT परिणाम का अनुसरण किससे किया जाना चाहिए?
A. Diagnostic confirmation with CVS (if early) or amniocentesis before definitive decision‑making
B. Immediate termination without confirmation
C. No further action required
D. Maternal dietary change only

10. Key counseling points about fetal biochemical screening should include: 10. भ्रूणीय बायोकेमिकल स्क्रीनिंग के बारे में प्रमुख परामर्श बिंदुओं में क्या शामिल होना चाहिए?
A. These are screening tests (not diagnostic), performance varies by test and gestation, results influenced by maternal factors, and positive screens need confirmatory diagnostic testing and counseling
B. They diagnose all fetal anomalies with 100% accuracy
C. No follow‑up is necessary after screening
D. Only maternal shoe size matters