First trimester screening for trisomy 21: Do the parameters used detect more pathologies than just Down syndrome?

Abstract

Objective: To assess the value of first trimester maternal serum free β human chorionic gonadotropin (β hCG), pregnancy-associated plasma protein (PAPP-A) concentrations and nuchal translucency (NT) as predictors of pregnancy complications. Design: A retrospective collaborative study of β hCG, PAPP-A and NT between 10 and 14 weeks of pregnancy in patients in whom pregnancy was followed to term. Nuchal translucency, maternal serum PAPP-A and free β hCG concentrations were measured in 1779 women with singleton pregnancies and without aneuploidies. Individual values were expressed as multiple of medians (MoM). Normal and abnormal pregnancies were compared for these parameters. Results: Irrespective of the presence or absence of pregnancy-associated pathologies; there was no change in the median MoM for NT. The median MoM for free β hCG was significantly increased in women with threatened abortions whereas the median MoMs for PAPP-A in women with spontaneous abortions or with pre-term deliveries were decreased significantly compared to normal pregnancies. These parameters have however no clinical usefulness as determined by receiver operator characteristics curves. Conclusion: Since PAPP-A is a protease that specifically degrades insulin-like growth factor binding proteins we would conclude that the control of the insulin-like growth factor system in the first trimester of pregnancy might play a key role in determining subsequent pregnancy outcome.