ObjectiveTo investigate the association between adverse perinatal outcomes and abnormal elevations of serum marker levels (alpha-fetoprotein [AFT] and free β-hCG) or a falso-positive screen for Down syndrome.MehtodsPregnancy outcome information was available for 5885 Taiwanese women under 35 years of age who had second-trimester maternal serum screening for Down syndrome, using AFP and free β-hCG, and delivered a chromosomally normal fetus. Those with AFT at least 2.0 multiples of the median (MoM), free β-hCG at least 2.5 MoM, or a false-positive screen (risk ratio at least 1:270) were identified, and the risk for adverse perinatal outcome was assessed.ResultsA serum AFP level at least 2.0 MoM (n= 176, 3.0%) was sognificantly associated with the occurrence of preterm delivery, low Apgar scores, small-for-gestationa-age infants, low birth weight or very low birth weight, fetal death, premature rupture of membranes, oligohydramnios, and a higher incidence of perinatal mortality. a serum free β-hCG level at least 2.5 Mom (n= 416, 7.1%) was significantly associated with low birth weight, an abnormally adherent placementa, and the occurrence of meconium-stained amniotic fluid. A higher incidence of fetal structural anomalies other than neural tube or abdominal wall defects, large-for-gestational-age infants, and postpartum hemorrhage was observed for a calculated risk of at least 1:270 (n= 311, 5.3%) independent of the other biochemical markers.ConclusionAsian women with unexplained elevations of serum AFP or free β-hCG, of a false-positive screen for Down syndrome are at increased risk for various adverse perinatal outcomes. Careful fetal ultrasound examination and thoughtful stragtegy for perinatal management are warranted for these patients.