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Updated: May 30, 2026
Microsatellite DNA Genotyping and Flow Cytometry Ploidy Analyses of Formalin-fixed Paraffin-embedded Hydatidiform Molar Tissues
Published on: October 20, 2019
Quantification of free fetal DNA in multiple pregnancies and relationship with chorionicity
George Attilakos1, Deborah G Maddocks, Teresa Davies
1Fetal Medicine Unit, St Michael's Hospital, University Hospitals Bristol NHS Foundation Trust, Bristol, UK. georgeattilakos@doctors.org.uk
Objective:
Free fetal DNA (ffDNA) in the maternal plasma appears to originate mainly from the trophoblast. We tested the hypothesis that ffDNA concentration is increased in multiple pregnancies where trophoblastic mass has been shown to be increased.
Methods:
Quantitative real-time PCR was used to measure the plasma concentration of DYS14 in singleton and twin pregnancies with one or two male fetuses. Royston and Wright's regression method was used to relate ffDNA to gestational age in singleton controls; z-scores were calculated for the multiple pregnancy subgroups.
Results:
Fifty-five singleton and 65 twin pregnancies (36 with one and 29 with two male fetuses) were analysed. There was significantly higher ffDNA concentration in twin pregnancies with two male fetuses compared with pregnancies with one male fetus. In cases with two male fetuses, there was no statistically significant difference between monochorionic and dichorionic pregnancies.
Conclusions:
There is higher ffDNA concentration in multiple pregnancies, and this must be taken into account for future quantitative ffDNA applications.
