False positive results of trisomy 21 prenatal screening as a surrogate marker for adverse pregnancy outcome

Abstract

IntroductionHypertensive disorders of pregnancy, intrauterine growth restriction (IUGR) and preterm delivery are pathologies associated with significant fetal and maternal morbidity and mortality. This study evaluates the usefulness of false positive results for trisomy 21 prenatal screening and isolated changes in biochemical screening markers for the identification of increased risk for those pregnancy complications. MethodTwo case–control studies were performed: the association of those pathologies with a false positive screening (Integrated or Double) and the distribution of the biochemical markers, PAPP-A, free beta-hCG and alpha-Fetoprotein (AFP), in affected and unaffected pregnant women. The population included all the 4224 pregnant women who underwent prenatal screening for trisomy 21 in Hospital S. Francisco Xavier, Lisbon, between March 2003 and August 2007. ResultsThe association was significant (P<0.05) between IUGR and false positives for Integrated and 2nd trimester screening and between IUGR and isolated changes in the three biochemical markers. Isolated changes of PAPP-A and AFP were significantly associated with preterm delivery and hypertensive disorders of pregnancy, respectively. ConclusionScreening false positive results or isolated changes in biochemical screening markers are surrogate markers of increased risk for placental pathology. This information is available before 20 weeks of gestation and can be used in follow-up.