Fig 1.
Early embryonic development from zygote to blastocyst.
The cytotrophoblast which is studied in short-term cultured villi (STC-villi) and with NIPT is derived from the trophoblast of the blastocyst, whereas the mesenchymal core, investigated in long-term cultured villi (LTC-villi) originates from the extra-embryonic mesoderm (EEM). Both EEM and fetus are derived from the inner cell mass (ICM) of the blastocyst.
Table 1.
Number of fetal trisomy 13, 18 and 21 cases amongst 5967 CV samples with karyotypically normal results or low-level mosaicism <30% in STC-villi.
Table 2.
Details of trisomy 21 cases with normal or low-mosaic (<30%) results in STC-villi in our cohort of 5967 CV samples.
Table 3.
Details of trisomy 18 cases with normal or low-mosaic (<30%) results in STC-villi in our cohort of 5967 CV samples.
Table 4.
False negative cytogenetic results in STC-villi involving trisomy 13, 18 and 21: literature review.