Are Down syndrome fetuses detected through maternal serum screening similar to those remaining undetected?

This study was designed to examine whether fetuses with Down syndrome (DS) identified through serum screening are different from those whose mothers have normal serum screening results. It was a retrospective follow-up study of pregnancies where maternal serum alpha-fetoprotein (MSAFP) concentrations were measured to identify women at increased risk of having a baby with a neural tube defect (NTD). An enhanced risk for NTD was the only reason for intervention in the screened population. Clinical features of fetuses or children with DS were related to the screening results. A retrospectively calculated term risk of 1/250 classified a pregnancy as having been at an elevated risk of DS. The outcome measures were fetal or neonatal death and severe somatic disease. Human chorionic gonadotrophin (hCG) and unconjugated oestriol (uE3) were measured retrospectively in frozen samples of the DS pregnancies and the same cut-off level was used for classification (so-called 'triple test'). Ten thousand women were included in the study. Pregnancy outcome was known in 93.5 per cent of the cases. Children with and without anatomic defects were found in all subgroups of test results combinations. All mothers of children with a congenital heart defect (CHD) had a DS risk of > or = 1/250 according to the triple test.