Maternal Smoking

OBJECTIVE: To estimate whether potential clinical applications of cell-free fetal and total DNA in the field of noninvasive prenatal diagnosis need to be adjusted for maternal smoking status. METHODS: In this study, using 344 maternal blood samples from the second trimester of pregnancy, circulating cell-free DNA in maternal plasma samples, specific for the SRY and DYS14 loci (representing fetal DNA) and GAPDH sequence (representing total genomic DNA) were quantified by real-time polymerase chain reaction. RESULTS: Fetal sex determination was 100% accurate using a combination of probes for SRY and DYS14. The levels of DYS14 and SRY detected were significantly correlated (r=0.884, P<.001). No significant difference was seen between the quantitative levels of cell-free male fetal DNA between the smoking groups and control group. Similarly, no significant difference was seen in the amount of total cell-free DNA in the study population. CONCLUSION: In contrast to first- and second-trimester screening assays for Down syndrome, where smoking status significantly affect levels of maternal serum analytes, smoking status does not affect quantitative levels of cell-free fetal DNA or total cell-free DNA in maternal plasma. LEVEL OF EVIDENCE: II.