Screening for Down's syndrome using an iso-risk curve based on maternal age and serum alpha-fetoprotein level.
On the basis of the significantly different distributions of maternal serum alpha-fetoprotein (AFP) levels in 86 pregnancies associated with fetal Down's syndrome and in 2018 unaffected pregnancies, an iso-risk curve for Down's syndrome was constructed. An iso-risk curve shows, for women of all ages, which combinations of maternal age and level of maternal serum AFP result in the same risk of carrying a fetus with Down's syndrome. A 1:400 risk of Down's syndrome, corresponding to the risk of a 35-year-old woman, was chosen as the lowest risk indicating referral for amniocentesis. If all women, irrespective of their age, are offered amniocentesis, when their risk of carrying a Down's syndrome fetus is 1:400 or higher, 53% of the affected fetuses can be detected as compared with 28% of the affected fetuses diagnosed at present in women above 35 years of age.
D000328:Adult; D004314:Down Syndrome / Q000175:diagnosis*; D005260:Female; D005315:Fetal Diseases / Q000175:diagnosis*; D006801:Humans; D008423:Maternal Age; D011247:Pregnancy; D018566:Pregnancy, High-Risk; D011296:Prenatal Diagnosis / Q000379:methods*; D012306:Risk; D000509:alpha-Fetoproteins / Q000032:analysis*
D000509:alpha-Fetoproteins