Abstract
To explore the rules for free fetal DNA clearance after delivery of fetuses carrying chromosomal aneuploidies. For 10 women carrying 18-to-25-gestation-week singletons confirmed to have chromosomal abnormalities by amniotic karyotyping, 5 mL of peripheral venous blood was drawn respectively before and 15 minutes, 30 minutes, 60 minutes, 120 minutes, 3 hours, 6 hours, 9 hours, 12 hours, 24 hours, 48 hours and 72 hours after their elective termination of pregnancies. Free fetal DNA was isolated from the plasma and subjected to high throughput sequencing. Statistical analysis of the sequence information showed that the free DNA of fetuses with trisomy 21 or 18 was rapidly cleared after delivery. The average half-life was approximately 1.24 hours within the first 2 hours after delivery. It was then slowly cleared between 6 and 72 hours, with an average half-life of 11.70 hours. No fetal DNA was detectable 72 hours after delivery. Free fetal DNA rapidly decreases after delivery and will completely disappear by 72 hours. Above results may provide a basis for clinical application of the non-invasive detection of chromosomal aneuploidies during prenatal diagnosis.
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