OBJECTIVE: To estimate fetal fraction (FF) in monozygotic and dizygotic twin pregnancies. METHODS: Maternal plasma samples were obtained from 35 monochorionic twin pregnancies with male fetuses (monozygotic) and 35 dichorionic pregnancies discordant for fetal sex (dizygotic) at 11-13 weeks' gestation. Cell-free DNA was extracted and chromosome-selective sequencing with digital analysis of selected regions (DANSR™) was carried out. The fetal-fraction optimized risk of trisomy evaluation (FORTE™) algorithm was used to estimate FF using polymorphic alleles. In dizygotic twins the FORTE algorithm was modified to estimate the smallest FF contribution of the 2 fetuses. In both types of twins, FF was also determined by analysis of Y-chromosome sequences. RESULTS: In monozygotic twins, the median total FF was 14.0% (range 8.2-27.0%) and in dizygotic twins the median smallest FF was 7.9% (4.9-14.0%). There were significant associations in FF between the methods using polymorphic alleles and Y-chromosome sequences for both monozygotic (r=0.951, p<0.0001) and dizygotic (r=0.743, p<0.0001) twins. CONCLUSIONS: The study demonstrates the feasibility of an approach for cfDNA testing in twin pregnancies. This involves estimation of total FF in monozygotic twins and estimation of the lower FF of the 2 fetuses in dizygotic twins.
OBJECTIVE: To estimate fetal fraction (FF) in monozygotic and dizygotic twin pregnancies. METHODS: Maternal plasma samples were obtained from 35 monochorionic twin pregnancies with male fetuses (monozygotic) and 35 dichorionic pregnancies discordant for fetal sex (dizygotic) at 11-13 weeks' gestation. Cell-free DNA was extracted and chromosome-selective sequencing with digital analysis of selected regions (DANSR™) was carried out. The fetal-fraction optimized risk of trisomy evaluation (FORTE™) algorithm was used to estimate FF using polymorphic alleles. In dizygotic twins the FORTE algorithm was modified to estimate the smallest FF contribution of the 2 fetuses. In both types of twins, FF was also determined by analysis of Y-chromosome sequences. RESULTS: In monozygotic twins, the median total FF was 14.0% (range 8.2-27.0%) and in dizygotic twins the median smallest FF was 7.9% (4.9-14.0%). There were significant associations in FF between the methods using polymorphic alleles and Y-chromosome sequences for both monozygotic (r=0.951, p<0.0001) and dizygotic (r=0.743, p<0.0001) twins. CONCLUSIONS: The study demonstrates the feasibility of an approach for cfDNA testing in twin pregnancies. This involves estimation of total FF in monozygotic twins and estimation of the lower FF of the 2 fetuses in dizygotic twins.
Authors: Luigi Carbone; Federica Cariati; Laura Sarno; Alessandro Conforti; Francesca Bagnulo; Ida Strina; Lucio Pastore; Giuseppe Maria Maruotti; Carlo Alviggi Journal: Genes (Basel) Date: 2020-12-24 Impact factor: 4.096
Authors: Sebastian Grömminger; Erbil Yagmur; Sanli Erkan; Sándor Nagy; Ulrike Schöck; Joachim Bonnet; Patricia Smerdka; Mathias Ehrich; Rolf-Dieter Wegner; Wera Hofmann; Markus Stumm Journal: J Clin Med Date: 2014-06-25 Impact factor: 4.241