Used in clinical and research laboratories to measure free estriol levels in human biological samples, particularly in maternal serum during pregnancy. The kit supports prenatal screening, especially for assessing fetal development and placental function. It is commonly used in triple or quadruple screening panels to evaluate the risk of chromosomal abnormalities such as Down syndrome (Trisomy 21) and Edwards syndrome (Trisomy 18). Due to its high sensitivity and specificity, the assay enables early detection and monitoring of pregnancy-related complications including intrauterine growth restriction and preterm birth risk. Widely applied in obstetric research and epidemiological studies focusing on hormonal changes during gestation.