Second Trimester Screening Tests Explained
The second trimester of pregnancy (weeks 14–27) is an exciting stage where your baby is growing rapidly. It’s also a crucial period for prenatal screening tests, which help evaluate the baby’s development and detect potential genetic or structural concerns.
After the first trimester screening, parents often wonder what comes next. The second trimester screenings provide further insights into the baby’s health and guide doctors in planning care.
👉 Also Read: First Trimester Prenatal Screening: What to Expect
What is Second Trimester Prenatal Screening?
Second trimester screening refers to a series of blood tests and ultrasounds performed between 15 and 22 weeks of pregnancy.
These tests help detect:
- Chromosomal conditions (e.g., Down syndrome, Trisomy 18)
- Neural tube defects (e.g., spina bifida)
- Certain birth defects (heart, abdominal wall, kidneys)
Types of Second Trimester Screening Tests
✅ 1. Quad Screen (Maternal Serum Screening)
- A blood test done between 15–22 weeks.
- Measures four substances in the mother’s blood:
- Alpha-fetoprotein (AFP)
- Human chorionic gonadotropin (hCG)
- Estriol
- Inhibin-A
- Abnormal results may suggest risk of Down syndrome, Edwards syndrome, or neural tube defects.
✅ 2. Level 2 Ultrasound (Anatomy Scan/Anomaly Scan)
- Performed between 18–22 weeks.
- Examines the baby’s organs, bones, brain, spine, and heart.
- Detects structural abnormalities like cleft lip, heart defects, kidney issues, and limb differences.
✅ 3. Targeted Tests (If Needed)
- If results are concerning, doctors may recommend additional tests such as amniocentesis or fetal echocardiography.
👉 Learn More: Prenatal Screening vs Diagnostic Tests – Key Differences
When is Second Trimester Screening Done?
- Quad screen: Usually between 15–18 weeks for the best accuracy.
- Anatomy scan: Between 18–22 weeks of pregnancy.
Benefits of Second Trimester Screening
- ✅ Detects birth defects not seen in the first trimester.
- ✅ Identifies risk for chromosomal abnormalities.
- ✅ Helps doctors monitor baby’s growth and development.
- ✅ Provides reassurance when results are normal.
- ✅ Guides parents on whether additional diagnostic testing is needed.
Limitations of Second Trimester Screening
- ⚠️ Screening provides a risk estimate, not a definite diagnosis.
- ⚠️ False positives may cause unnecessary worry.
- ⚠️ Some abnormalities may only be detected later in pregnancy.
Understanding Your Results
Your doctor or genetic counselor will explain results as:
- Low risk: Baby is unlikely to have the conditions tested.
- High risk: Increased chance of a condition; follow-up tests may be recommended.
👉 Related Blog: Genetic Counseling for Pregnancy – Benefits & What to Expect
FAQs on Second Trimester Screening
Q1. Do I need second trimester screening if my first trimester screening was normal?
Yes — the two screenings provide different information and complement each other.
Q2. Is the anatomy scan the same as a gender scan?
The anatomy scan can reveal the baby’s gender, but its main purpose is to check organ development and detect abnormalities.
Q3. What happens if results are abnormal?
Your doctor may recommend further diagnostic tests like amniocentesis for confirmation.
Final Thoughts
The second trimester prenatal screening plays a vital role in ensuring your baby’s healthy development. With a combination of quad blood test and anatomy ultrasound, it provides valuable insights into genetic and structural conditions.
While it’s not diagnostic, the results guide parents and doctors in making informed decisions about pregnancy care.
👉 Next Read: Common Myths About Prenatal Screening
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