Diagnosis of fetal chromosomal aneuploidy by free fetal DNA in maternal plasma in the first trimester

Abstract

Objective To assess the clinical value of fetal chromosomal aneuploidy diagnosed by free fetal DNA in maternal plasma in 11-13+6 gestational weeks.Methods A total of 2 650 pregnant women who had prenatal care in Tianjin Center Hospital of Obstetrics and Gynecology from January 1,2010 to December 31,2010 were included.Each of them had an ultrasound scan to measure fetal nuchal translucency thickness.Maternal serum free β-human chorionic gonadotropin and pregnancy-associated plasma protein A test was performed as part of screening for chromosomal abnormalities.Results of ultrasound and maternal plasma biochemical analysis were entered into the database,and converted into multiple of median (MoM) by factors such as maternal age,weight,ethnicity,smoking history and mode of conception.The cutoff value was 1 ∶ 270.Meanwhile,20 cases had cell free fetal DNA (cffDNA) test and the ratio of the single nucleotide polymorphism on two alleles of plancenta-specific 4 (PLAC4) were measured in 16 cases.T-test,rank sum test,MannWhitney U test and Chi-square test were used as statistical methods.Results (1) A total of 74 cases were judged as high-risk,among which 35 cases underwent transabdominal chorionic villus sampling (18 cases had cffDNA test),37 cases underwent amniocentesis at the week of 20,and two cases of Rh negative did not receive the invasive examination.Totally 20 cases,including two Rh negative cases,had the cell-free fetal DNA test.(2) By cffDNA test of maternal plasma,two cases of 21 trisomy,one case of 18 trisomy,two cases of 45,XO and one case of balanced translocation were diagnosed.(3) In the two cases of 21 trisomy,maternal plasma G/A ratio ofPL4C4 RNA-single nucleotide polymorphism alleles was 1.00 (0.98,1.02) ; in 14 pregnancies with normal chromosome,the ratio was 1.055 (1.02,1.13,Z=3.5).There was no significant difference (P=0.066).Conclusion Diagnosing of fetal chromosomal aneuploidy by cffDNA in maternal plasma is feasible and noninvasive with high negative predictive value,and can be used in Rh-negative pregnant women for prenatal screening and diagnosis. Key words: Aneuploidy;  Prenatal diagnosis;  DNA;  Pregnancy trimester, first