22 Fetal down syndrome is associated with increased cell-free fetal DNA levels in archived maternal serum samples

OBJECTIVE: Increased cell-free fetal DNA levels in maternal circulation are a potential noninvasive marker for fetal Down syndrome.While several reports have shown an association between increased fetal DNA levels and trisomy 21 using fresh maternal plasma, a single study using serum has not.The objective of this study was to ascertain if fetal DNA levels are increased in pregnant women carrying fetuses with trisomy 21 using archived serum samples, using a larger number of paired control samples compared with prior studies.STUDY DESIGN: Routine nfidtrimester maternal serum screening samples were collected and stored at -20°C from 6 subjects carrying a singleton fetus with 47,XY,+21 karyotype.Each was matched and compared to 5 control samples (30 total) from mothers carrying presmned euploid male fetuses.Controls were matched for gestational age and date of collection.Fetal DNA concentration in maternal serum was quantified using real-time PCR amplification for a Y chromosomal sequence.A mixed model, repeated measures ANOVA was used for statistical analysis.RESULTS: The adjusted mean fetal DNA concentrations among women carrying trisomy 21 tetuses were 49.7 (95% CI 34.2-65.2) genomicequivalents/ml (GE/ml) and 30.4 (23.4-37.4)GE/ml among the controls (P= .027).Median values were 50.5 GE/ml mad 26.0 GE/ml, respectively.CONCLUSION: These data suggest that pregnancies complicated by fetal