Approximately 10% of DNA floating freely in a pregnant woman’s plasma originates from the fetus that she carries. Analysis of cell-free fetal DNA in maternal plasma has formed the basis for the development of noninvasive prenatal genetic diagnostics for detection of fetal trisomies and specific paternally inherited mutations. Kitzman et al. in this study reconstructed the whole-genome sequence of a human fetus using samples obtained noninvasively at 18.5 weeks of gestation (including DNA from the pregnant mother; DNA from the father; and ”cell-free” DNA from the pregnant mother’s plasma which represents a mixture of the maternal and fetal genomes). Kitzman et al. combined genome sequencing of the two parents, genome-wide maternal haplotyping, and deep sequencing of maternal plasma DNA to noninvasively determine the genome sequence of the human fetus.
At present, only a few specific genetic disorders are screened for during pregnancy and definitive diagnosis involves invasive procedures such as amniocentesis. Although technical limitations still remain to be overcome, this study suggests it may soon be possible to screen for all Mendelian disorders (collectively affecting ~1% of births) early in pregnancy.
Noninvasive whole-genome sequencing of a human fetus. Kitzman et al. Sci Transl Med. 2012 Jun 6;4(137):137ra76. PMID: 22674554
posted by Yannis Trakadis, MD