OBJECTIVES: To evaluate the feasibility of non-invasive prenatal testing (NIPT) 
of maternal plasma samples collected from pregnant Chinese women in early 
gestation, between 8 + 0 and 12 + 6 weeks' gestation.
METHODS: In this pilot study, 212 women with high-risk pregnancies were 
recruited at a single Chinese Hospital. Fetal aneuploidies associated with 
chromosomes 21, 18, 13, X and Y were detected by massively parallel sequencing 
of maternal plasma DNA samples. Invasive prenatal diagnosis by either chorionic 
villus sampling or amniocentesis and then karyotyping was offered to all women 
to confirm both positive and negative NIPT results. Fetal DNA fraction was also 
determined in male pregnancies, by the relative percentage of Y-chromosome 
sequences. All confirmed NIPT-negative pregnancies were followed up to birth and 
neonates were clinically evaluated for any symptoms of chromosomal disease.
RESULTS: Autosomal aneuploidies trisomy 21 (n = 2), 18 (n = 1) and 13 (n = 1) 
were detected by NIPT and confirmed by amniocentesis and karyotyping. There were 
one false-positive 45,X sample and two false-negative samples associated with 
fetal karyotypes 47,XXY and 45,X[16]/47,XXX[14]. In the 100 male pregnancies, 
the median fetal DNA fraction was 8.54% and there was a trend towards an 
increasing fetal fraction from 8 + 0 to 12 + 6 weeks' gestation. The majority 
(95%) of pregnancies had a fetal DNA fraction > 4%, which is generally the limit 
for accurate aneuploidy detection by NIPT. Across this early gestational time 
period, there was a weak inverse relationship (R(2)  = 0.186) between fetal DNA 
fraction and maternal weight.
CONCLUSIONS: NIPT is highly reliable and accurate when applied to maternal DNA 
samples collected from pregnant women in the first trimester between 8 + 0 and 
12 + 6 weeks.