PRISCA 1 - Пренатальный скрининг 1 триместр (11-13 неделя) (свободный β-ХГЧ+РАРР-А)

First-trimester prenatal trisomy screening (PRISCA I), also called the maternal serum first-trimester double test or Maternal Screen, First Trimester, estimates the probability of fetal chromosomal aneuploidy—principally trisomy 21 (Down syndrome) and trisomy 18 (Edwards syndrome). The risk algorithm merges maternal demographic and pregnancy data with first-trimester serum markers to yield a gestational age–specific risk; it is a screening tool and does not establish a diagnosis.

Human chorionic gonadotropin (hCG) is produced by chorionic tissue in early pregnancy. Serum hCG concentrations rise to a peak around weeks 10–11 and then gradually decline; abnormal values can reflect deviations in placental function and are incorporated into first‑trimester risk models. PRISCA‑based risk calculation requires precise gestational dating and complete maternal inputs to ensure valid multiples‑of‑the‑median (MoM) adjustments. Variables typically entered include maternal age, weight, number of fetuses, race/ethnicity, tobacco use, and pregestational diabetes, as well as applicable ultrasound findings. Incomplete or inaccurate clinical or ultrasound information can materially distort the computed risk. This is a screening, not a diagnostic, assessment. Elevated risk estimates may occur in the absence of fetal aneuploidy; for example, an increased free β‑hCG associated with placental dysfunction or threatened miscarriage can yield a high‑risk screen. Results should be interpreted in clinical context, and genetic counseling is recommended for guidance on next steps.