Cell Free Fetal and Total DNA Levels in Pregnancies at Risk of Sickle Cell Disease and Significant Ethnic Variation.

Cell free (cf) DNA in maternal circulation is increasingly investigated in pregnancy. We aimed to determine if sickle cell trait women had quantitative differences of cfDNA with controls and if there was an ethnic difference between the cfDNA levels of Northern European and African/African-Caribbean populations. Non-invasive prenatal diagnosis through quantification of fetal and total cfDNA was tested in 33 pregnant women at risk of carrying a fetus affected with sickle cell disease and 124 control pregnancies. Fetal cfDNA assays were based on two Y chromosome specific markers (SRY and DYS14) and total cfDNA was based on the β-globin gene on chromosome 11. Maternal age (MA), gestation age (GA), fetal sex, storage time prior to extraction, maternal weight and body mass index (BMI) before pregnancy were compared to the fetal and total cfDNA levels. No significant difference in the fetal or total cfDNA levels was found between any of the control pregnancies and the sickle cell trait mothers carrying HbAA, HbAS and HbSS fetuses. However, higher levels of total cfDNA, but lower fetal cfDNA levels were observed in the African/African-Caribbean population compared with the Nothern Europeans. A significant variation in cfDNA was found between ethnic groups, which should be taken under consideration in future studies measuring cfDNA.