Original Paper Fetal Diagn Ther 2013;33:215–223 DOI: 10.1159/000346806 Maternal Plasma Cell-Free Fetal and Maternal DNA at 11–13 Weeks’ Gestation: Relation to Fetal and Maternal Characteristics and Pregnancy Outcomes L.C.Y. Poon a T. Musci c K. Song c A. Syngelaki a K.H. Nicolaides a, b a Harris Birthright Research Centre for Fetal Medicine, King’s College Hospital, and b Department of Fetal Medicine, University College London Hospital, London, UK; c Ariosa Diagnostics, San Jose, Calif., USA racial origin than in Caucasians, and lower in smokers, but it was not significantly altered in pregnancies complicated by PE, SPB or SGA. The fetal cfDNA level was inversely related to maternal weight and uterine artery pulsatility index, and ma- ternal cfDNA increased with maternal weight. Conclusions: The fetal and maternal cfDNA level in maternal plasma is af- fected by maternal and fetal characteristics, but it is not al- tered in pregnancy complications. Copyright © 2013 S. Karger AG, Basel Introduction Analysis of cell-free DNA (cfDNA) in maternal blood can detect more than 99% of pregnancies with trisomy 21 at a false-positive rate of less than 1% [1–9]. Consequent- ly, this method is far superior to all currently available approaches to screening for trisomy 21 [10]. A potential issue with analysis of cfDNA as a universal screening test in all pregnant women is the failure rate in providing a result, which primarily depends on the relative propor- tion of fetal cfDNA to maternal cfDNA in maternal plas- ma. In trisomic pregnancies the number of molecules de- rived from the extra fetal chromosome, as a proportion of Key Words Cell-free fetal DNA · Cell-free maternal DNA · First-trimester screening · Preeclampsia · Small for gestational age · Preterm birth Abstract Objective: To examine the possible relationship between maternal and fetal characteristics and pregnancy outcomes on fetal and maternal cell-free (cf) DNA in maternal plasma at 11–13 weeks’ gestation. Methods: cfDNA was extracted from maternal plasma of 1,949 singleton pregnancies and chromosome-selective sequencing was used to determine the proportion of cfDNA and total cfDNA counts which was of fetal and maternal origin. Multivariate regression analysis was used to determine whether specific maternal and fetal characteristics and pregnancy complications, such as pre- eclampsia (PE), early spontaneous preterm birth (SPB) and delivery of small for gestational age (SGA) neonates, were significant predictors of fetal and maternal cfDNA in mater- nal plasma. Results: The fetal and maternal cfDNA plasma concentration increased with serum pregnancy-associated plasma protein-A and free β-human chorionic gonadotropin level, was higher in women of Afro-Caribbean and East-Asian Received: December 26, 2012 Accepted after revision: January 4, 2013 Published online: March 5, 2013 Prof. K.H. Nicolaides Harris Birthright Research Centre for Fetal Medicine King’s College Hospital, Denmark Hill London SE5 9RS (UK) E-Mail kypros  @  fetalmedicine.com © 2013 S. Karger AG, Basel 1015–3837/13/0334–0215$38.00/0 E-Mail karger@karger.com www.karger.com/fdt Downloaded by: UCL 82.23.63.209 - 2/17/2014 8:01:18 PM