P-211: Quantitative Changes of Fetal DNA in Maternal Circulation during Pregnancy Based on Detection of SRY Gene in Ovine Species

Background: It is well documented that fetal DNA can cross the placenta and is present in peripheral maternal blood during pregnancy in human. This fetal DNA also named circulating cell free fetal DNA, has emerged as a valuable source for genetic evaluation. Compared with humans, ovine species have a different structure of placental (synepitheliochorial) with no direct contact between the trophoblast and the maternal blood, hence, it is likely that the passage of fetal DNA to the ovine maternal blood would be scarce. This study is carried out to quantify the amount of fetal DNA in maternal blood plasma during pregnancy using quantitative real-time PCR (qPCR). Materials and Methods: Fetal DNA was isolated from blood plasma of 46 pregnant ewes during the second to fifth month of gestation. Real-time quantitative PCR technique was used to evaluate the quantitative changes of fetal DNA during pregnancy based on detection of SRY gene.Results: The SRY 286-base pair fragment was detected in all samples with male pregnancies, but no female pregnancies. The sensitivity and specificity of tests were 100% with no false negative or false positive results. It was also determined that fetal DNA levels are significantly increased during pregnancy, up to approximately 1.65-fold in the last 2 months of pregnancy (p< 0.05). Conclusion: The results of quantitative analysis demonstrated a significant increase in the amount of fetal DNA in maternal circulation in later stages of pregnancy.