Free fetal DNA concentration in maternal plasma during normal labour at term

OBJECTIVE: Our aim was to investigate the effect of uterine contractions on free fetal DNA concentration in maternal plasma at term. STUDY DESIGN: Nine pregnant women were admitted for elective induction of labour between 38 and 40 weeks of gestation. All patients carrying male fetuses and without history of pre-term labour and membrane rupture were selected. Maternal venous blood samples were serially collected every hour during labour, one hour after delivery and 24 h after delivery. In order to amplify fetal and total free DNA, primers for SRY and GAPDH genes were respectively chosen. Real- time PCR analysis was performed with an GeneAmp 5700 Sequence Detection System (Applied Biosystems Foster City, USA). Statistical significance was determined using the Wilcoxon test. RESULT: Median concentration of fetal DNA in plasma before labour was 3081 copies/mL (Range 812-15 864 copies/mL). No significant difference between the number of copies per millilitre before any contractions and during labour was demonstrated.One hour after delivery, significant decrease in the fetal DNA rate was observed with a median concentration of 293 copies/mL (Range 0-2037 copies/mL) (p-value: 0.04).This drop was more significant 24 h after delivery with a median concentration of 0 copies/mL (Range 0-95 copies/mL) (p-value: 0.02). CONCLUSIONS: During labour, no changes in free fetal DNA in maternal plasma were demonstrated. This suggests that labour does not have effect on free fetal DNA release in maternal circulation at term.