Genetic Pregnancy Screening Tests: A Comprehensive Guide for Expectant Mothers

Early detection of chromosomal or genetic abnormalities. By analyzing fetal DNA through maternal blood or imaging methods, these tests help parents make more informed decisions about pregnancy. In this article, we discuss **types of tests, time, accuracy, advantages and disadvantages** as well as **ethical considerations** of genetic screening.

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**1. Types of genetic screening tests in pregnancy** ### **a) First trimester screening (weeks 11-13)** - **Double Marker test:** - Measurement of two substances in mother's blood: **PAPP-A** and **Free β-hCG**. - Combination with ultrasound **NT (thickness of the back of the neck of the fetus)** to increase accuracy. - Diagnosing the risk of Down syndrome (trisomy 21) and trisomy 5 1 ### **b) Second trimester screening (week 22-14)** - **Quadruple Marker test:** - Measurement of **AFP, hCG, Estriol, Inhibin A**. - Identify the risk of Down syndrome, neural tube defects (NTD), and trisomy - **Anomalous ultrasound:** Examining fetal structures (heart, spine, organs) ### **c) non-invasive tests (NIPT/cfDNA)** - **Cell-free DNA test (NIPT):** - Fetal DNA analysis in mother's blood from **week 10 of pregnancy**. - Accuracy **>99%** for trisomies 21, 18, and 13 and sex chromosome disorders - Suitable for high-risk women (old age, family history). ### **d) invasive diagnostic tests** - **Amniocentesis (weeks 15-20):** Sampling of amniotic fluid to check chromosomes - **CVS (weeks 11-14):** placental villi sampling to diagnose hereditary diseases such as thalassemia

**2. Benefits of genetic screening** ✅ **Early diagnosis:** Identification of abnormalities before birth. ✅ **Non-invasiveness (NIPT):** No risk of miscarriage. **Pregnancy management:** Planning for special care or treatments after birth. ✅ **Reducing anxiety:** Ensuring the health of the fetus in cases of negative results **3. Limitations and challenges** ❌ **False positive result:** Some tests (such as NIPT) require confirmation with amniocentesis. ❌ **High cost:** Advanced tests like NIPT may not be covered by insurance. ❌ **Ethical issues:** Deciding on the continuation of pregnancy in positive cases **4. Who should be screened?** - Women over 35 years old. - Family history of genetic defects (such as Down syndrome). - Abnormal results in ultrasound or previous tests **5. Interpretation of results** - **Low risk:** The probability of abnormality is low (does not require follow-up). - **Moderate/high risk:** Recommendation for diagnostic tests (amniocentesis or CVS) **6.