Recent advances in Down syndrome screening

Maternal serum screening for Down syndrome has been developed since 1994 in Taiwan. A prospective collaborative study has been conducted in Taiwan to compare the two-analyte screening strategy combining serum alpha-fetoprotein (AFP), either with total human chorionic gonadotropin (hCG) or free β-hCG, and with maternal age. The results confirmed that maternal serum screening for Down syndrome could also achieve a 60% detection rate at a 5% false-positive rate in Asians. In addition, abnormal elevation of serum markers for Down syndrome screening has been reported to be associated with adverse pregnancy outcomes. Thus, women with unexplained elevations of serum markers at increased risk for various adverse outcomes. Careful fetal ultrasound examination and thoughtful strategy for perinatal management are recommended for these patients. There are several benefits including no invasion, easy collection and high acceptability by using urine instead of serum. Our previous studies confirmed that maternal urine screening for Down syndrome using free β-hCG or beta core fragment of hCG (β-core) in combination with total estriol (E₃) during the second trimester are feasible in Asians with a detection rate at 60-80%. The measurement of fetal nuchal translucency (NT) thickness has been developed for first-trimester Down syndrome screening since 1992. This screening policy could achieve an 82% detection rate at an 8% false-positive rate. However, wide variation and conflicting results of the sensitivity of this marker enables this screening method for further evaluation of its value in general practice.