title: Effects of Maternal and Fetal Characteristics on Cell-Free Fetal DNA Fraction in Maternal Plasma.
abstract: OBJECTIVE
  To study factors that influence the concentration of cell-free fetal DNA (fetal fraction) using a large clinical data set of pregnancies with male fetus.
  
  
  METHODS
  A retrospective analysis of 23 067 pregnancies that received noninvasive prenatal testing from January 2012 to October 2013, including 22 650 normal singleton pregnancies (control group) and 417 pregnancies with aneuploidy, twin pregnancy, or various maternal conditions including preexisting hypertension, preexisting diabetes, hyperthyroidism, and carrier of the surface antigen of the hepatitis B virus (HBsAg; study group). Multiples of the median (MoM) analysis was performed in the control group to derive gestation and body mass index (BMI)-corrected fetal fraction. The effects of study group conditions on fetal fraction were examined by calculating the ratio of MoM (RMoM) values.
  
  
  RESULTS
  Fetal fraction showed a positive correlation with gestational age (r(2) = .10, P < .001) and increased rapidly after the 21 weeks of gestation (r(2) = .26, P < .001). Negative association with maternal BMI was found with fetal fraction (r(2) = .04, P < .001). In study group, fetal fraction was higher among pregnant women with a trisomy 21 fetus (RMoM = 1.24, P < .001) and lower among trisomy 18 (RMoM = 0.84, P < .001). A 1.6-fold incensement of fetal fraction was observed in twin fetuses comparing to singleton pregnancy (RMoM = 1.62, P < .001). Women with preexisting hypertension had significantly lower fetal fraction (RMoM = 0.85, P = .02). Preexisting diabetes, hyperthyroidism, or carrier of HBsAg did not affect fetal fraction.
  
  
  CONCLUSIONS
  The fetal fraction was affected by fetal aneuploidy, maternal BMI, and the number of gestation. Maternal preexisting of hypertension appeared to reduce fetal fraction.
authors.affiliation: Fetal Medicine Center, First Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong Province, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Clinical Laboratory of BGI Diagnostics, BGI-Shenzhen, Shenzhen, China.
authors.forename: Zhongyi
authors.initials: Z
authors.lastname: Zhu
authors.affiliation: Clinical Laboratory of BGI Diagnostics, BGI-Shenzhen, Shenzhen, China.
authors.forename: Ya
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Clinical Laboratory of BGI Diagnostics, BGI-Shenzhen, Shenzhen, China.
authors.forename: Yuying
authors.initials: Y
authors.lastname: Yuan
authors.affiliation: Clinical Laboratory of BGI Diagnostics, BGI-Shenzhen, Shenzhen, China.
authors.forename: Yulai
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Clinical Laboratory of BGI Diagnostics, BGI-Shenzhen, Shenzhen, China.
authors.forename: Lijun
authors.initials: L
authors.lastname: Zhou
authors.affiliation: Clinical Laboratory of BGI Diagnostics, BGI-Shenzhen, Shenzhen, China.
authors.forename: KaiKai
authors.initials: K
authors.lastname: Liao
authors.affiliation: Clinical Laboratory of BGI Diagnostics, BGI-Shenzhen, Shenzhen, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.affiliation: Clinical Laboratory of BGI Diagnostics, BGI-Shenzhen, Shenzhen, China.
authors.forename: Bole
authors.initials: B
authors.lastname: Du
authors.affiliation: Clinical Laboratory of BGI Diagnostics, BGI-Shenzhen, Shenzhen, China.
authors.forename: Yumei
authors.initials: Y
authors.lastname: Hou
authors.affiliation: Clinical Laboratory of BGI Diagnostics, BGI-Shenzhen, Shenzhen, China.
authors.forename: Zhonglin
authors.initials: Z
authors.lastname: Chen
authors.affiliation: BGI-Research, BGI-Shenzhen, Shenzhen, China Shenzhen Birth Defect Screening Project Lab, BGI-Shenzhen, Shenzhen, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Chen
authors.affiliation: Clinical Laboratory of BGI Diagnostics, BGI-Shenzhen, Shenzhen, China.
authors.forename: Hongyun
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Clinical Laboratory of BGI Diagnostics, BGI-Shenzhen, Shenzhen, China.
authors.forename: Cong
authors.initials: C
authors.lastname: Yu
authors.affiliation: Clinical Laboratory of BGI Diagnostics, BGI-Shenzhen, Shenzhen, China.
authors.forename: Lijian
authors.initials: L
authors.lastname: Zhao
authors.affiliation: Fetal Medicine Centre, Paramount Medical Centre, Hong Kong.
authors.forename: T K
authors.initials: TK
authors.lastname: Lau
authors.affiliation: Clinical Laboratory of BGI Diagnostics, BGI-Shenzhen, Shenzhen, China jiangfuman@genomics.cn wangw@genomics.cn.
authors.forename: Fuman
authors.initials: F
authors.lastname: Jiang
authors.affiliation: Clinical Laboratory of BGI Diagnostics, BGI-Shenzhen, Shenzhen, China BGI-Research, BGI-Shenzhen, Shenzhen, China Shenzhen Birth Defect Screening Project Lab, BGI-Shenzhen, Shenzhen, China jiangfuman@genomics.cn wangw@genomics.cn.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D000328:Adult; D000782:Aneuploidy; D015992:Body Mass Index; D004247:DNA / Q000097:blood / Q000235:genetics*; D005260:Female; D005333:Fetus / Q000378:metabolism*; D005819:Genetic Markers; D005820:Genetic Testing; D005865:Gestational Age; D006801:Humans; D006973:Hypertension / Q000097:blood / Q000175:diagnosis / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011247:Pregnancy; D059285:Pregnancy, Twin / Q000097:blood / Q000235:genetics; D011296:Prenatal Diagnosis / Q000379:methods*; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D005819:Genetic Markers; D004247:DNA
keywords: body mass index; fetal fraction; gestational age; multiples of the median.; preexisting hypertension; twin pregnancy