Беременность - пренатальный скрининг трисомий II триместра беременности, PRISCA

Prenatal Second-Trimester Screening (triple test; PRISCA) evaluates maternal serum to estimate the probability of fetal trisomy 21, trisomy 18, and open neural tube defects. This screening result supports risk stratification and genetic counseling and helps determine whether additional ultrasound assessment or diagnostic testing is warranted.

This second-trimester maternal serum screen—commonly referred to as the triple test or PRISCA—combines risk modeling with clinical inputs to estimate the likelihood of trisomy 21, trisomy 18, and open neural tube defects. It is a screening tool, not a diagnostic assay; results quantify risk and are interpreted alongside ultrasound findings and clinical history. Human chorionic gonadotropin (hCG) is produced by trophoblastic tissue, peaks around weeks 10–11 of gestation, and then declines. Alpha-fetoprotein (AFP) originates from the fetal yolk sac, liver, and gastrointestinal epithelium; maternal serum AFP rises from approximately week 10 and reaches its highest concentrations at 30–32 weeks. Unconjugated estriol (uE3) reflects fetoplacental function; low uE3 together with elevated β-hCG and AFP is associated with increased risk of fetal growth restriction and third-trimester complications, including placental abruption and preeclampsia. Accurate gestational age and complete maternal data (e.g., age, weight, plurality, race/ethnicity, smoking status, and diabetes) are essential because marker medians and calculated risks vary with these variables. False-positive high-risk estimates can occur when β-hCG is increased in the setting of placental dysfunction or threatened abortion. For neural tube defect prevention, the World Health Organization recommends folic acid supplementation at 400 mcg/day for women planning pregnancy beginning 2–3 months before conception and continuing through the first trimester.