Noninvasive prenatal testing for fetal aneuploidies in the first trimester of pregnancy.

Song Y1, Huang S, Zhou X, Jiang Y, Qi Q, Bian X, Zhang J, Yan Y, Cram DS, Liu J.

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Abstract

OBJECTIVES:

To evaluate the feasibility of noninvasive prenatal testing (NIPT) on maternal plasma samples collected from 212 pregnant Chinese women at 8-12 weeks gestational age.

METHODS:

Women with high-risk pregnancies were prospectively recruited for the study at a single Chinese Hospital. Fetal aneuploidies associated with Chr 21, 18, 13, X and Y were detected by massively parallel sequencing of their maternal plasma DNA samples. Invasive prenatal diagnosis by either CVS or amniocentesis and then karyotyping was offered to all women to confirm both NIPT positive and negative results. All confirmed NIPT negative pregnancies were followed to birth and neonates clinically evaluated for any symptoms of chromosome disease.

RESULTS:

Autosomal aneuploidies T21 (n = 2), T18 (n = 1) and T13 (n = 1) were detected by NIPT and confirmed by amniocentesis and karyotyping. There was one false positive 45,X sample and two false negative samples associated with fetal karyotypes 47,XXY and 45X[16]/47,XXX[14]. The median DNA fraction was 8.54% and there was a trend towards an increasing fetal DNA fraction from 8 to 12 weeks gestation. The majority of pregnancies (95%) had a fetal DNA fraction of more than 4% which is the general limit of NIPT for accurate aneuploidy detection. Across the early gestational window, there was a weak inverse relationship (R2 = 0.186) between fetal DNA fraction and maternal weight.