Correlation of maternal age and combined assessments on risk of chromosomal anomaly during prenatal screening

Abstract

Background: Prenatal detection of genetic abnormalities is one of the biggest challenges of current fetal medicine. Prenatal screening for chromosomal abnormalities can be done using biochemical tests. The screening is a risk estimation test and not a diagnostic test. Methods: Statistical data treatment had been performed on a sample of 362 pregnant women for prenatal screening. This was a retrospective data analysis study undertaken at the National Reference Laboratory, Redcliffe Labs. Results: Nine (2.48%) women out of 362 were screen positive for chromosomopathy. The point biserial correlation between variables (Free β-hCG - Free Beta Human Chorionic Gonadotrophin, PAPP-A- pregnancy associated plasma protein-A and NT-(nuchal translucency) amongst patients with positive and negative screen test was statistically significant. There was a positive correlation between positive screen for chromosomopathy and hCG, MoM, NT MoM whereas a negative correlation between them and PAPP-A. This study indicates that higher values of hCG and lower values of PAPP-A MoM as seen in the positive screen patients is associated with a significant risk of chromosomopathy. A positive correlation between age and screen positive cases was seen. The McNemar’s test indicated a significant reduction in screen positive cases when biomarkers were added to screen for Trisomy 21 in women aged >35 years (n=86). 81 women eventually screened negative. Conclusions: The analyses stresses on the importance of using state-of-the-art, prenatal noninvasive screening software to help provide a predictive outcome, individualized for that pregnant woman.