The test is performed during the second trimester (15–20 weeks) of pregnancy.

It helps estimate the risk of:

Down syndrome (Trisomy 21)

Edwards syndrome (Trisomy 18)

Neural tube defects (e.g., spina bifida, anencephaly)

Clinical uses include:

Screening for chromosomal abnormalities.

Identifying pregnancies that may require further diagnostic testing (e.g., amniocentesis).

Supporting prenatal counseling and risk assessment.

Often performed alongside Ultrasound, Quadruple Marker Test, and Non‑invasive Prenatal Testing (NIPT) for comprehensive evaluation.

Analytes:

Alpha‑fetoprotein (AFP): Protein produced by the fetal liver.

Human Chorionic Gonadotropin (hCG): Hormone produced by the placenta.

Unconjugated Estriol (uE3): Estrogen produced by the placenta and fetal liver.

Normal Range: Values vary depending on gestational age.

Abnormal Findings:

High AFP: Suggests neural tube defects or abdominal wall defects.

Low AFP + High hCG + Low uE3: Suggests Down syndrome.

Low AFP + Low hCG + Low uE3: Suggests Edwards syndrome.

Clinical Use:

Provides a risk assessment, not a definitive diagnosis.

Helps guide further testing and prenatal management.

Supports obstetrics and maternal‑fetal medicine evaluations.