Gestational age and maternal weight effects on fetal cell-free DNA in maternal plasma

• Published in: Prenatal diagnosis Vol. 33; no. 7; pp. 662 - 666
• Main Authors: Wang, Eric, Batey, Annette, Struble, Craig, Musci, Thomas, Song, Ken, Oliphant, Arnold
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01-07-2013; Wiley Subscription Services, Inc
• Subjects: Body Weight; DNA - blood; Female; Fetus - chemistry; Genetic Testing - methods; Gestational Age; Humans; Polymorphism, Single Nucleotide - genetics; Pregnancy; Prenatal Diagnosis - methods
• ISSN: 0197-3851; 1097-0223
• DOI: 10.1002/pd.4119

ABSTRACT
Objective
To determine the effects of gestational age and maternal weight on percent fetal cell‐free DNA (cfDNA) in maternal plasma and the change in fetal cfDNA amounts within the same patient over time.
Methods
The cfDNA was extracted from maternal plasma from 22 384 singleton pregnancies of at least 10 weeks gestation undergoing the HarmonyTM Prenatal Test. The Harmony Prenatal Test determined fetal percentage via directed analysis of cfDNA.
Results
At 10 weeks 0 days to 10 weeks 6 days gestation, the median percent fetal cfDNA was 10.2%. Between 10 and 21 weeks gestation, percent fetal increased 0.1% per week (p < 0.0001), and 2% of pregnancies were below 4% fetal cfDNA. Beyond 21 weeks gestation, fetal cfDNA increased 1% per week (p < 0.0001). Fetal cfDNA percentage was proportional to gestational age and inversely proportional to maternal weight (p = 0.0016). Of 135 samples that were redrawn because of insufficient fetal cfDNA of the initial sample, 76 (56%) had greater than 4% fetal cfDNA in the sample from the second draw.
Conclusion
Fetal cfDNA increases with gestation, decreases with increasing maternal weight, and generally improves upon a blood redraw when the first attempt has insufficient fetal cfDNA. © 2013 John Wiley & Sons, Ltd.
What's already known about this topic?
Previous literature indicates no significant change in average percentage of fetal cell‐free DNA between 10 and 22 weeks when using Next‐Generation Sequencing technology.
What does this study add?
This is the largest sample set reporting changes in percent fetal cell‐free DNA in relation to maternal weight and gestational age.