Objective  To establish a basis for genetic counseling and prenatal gene diagnosis of Duchenne muscular dystrophy (DMD).    Methods  Three pregnant DMD carriers visited our department and their fetal gender was determined by sex determining gene primer polymerase chain reaction (PCR) and cell karyotyping of amniotic fluid. The genomic DNA was extracted from the peripheral blood of the family members with DMD and fetal amniotic fluid or fetal umbilical vein blood. Then multiplicitas prime PCR and polyacrylamide gel method were used to analyze the polymorphism of the (CA)n short tandem repeat (STR) in 3′ end and in the introns 44

45

49

50 of DMD gene.   Results  In the 4 fetuses

two singleton fetus and one of the twins were male

the other of twins was female. Gene deletion occurred in one pedigree and non-gene deletion in the other two pedigrees. Four fetuses had the same haploid of proband inherited from their mothers. The female fetus of the twins was risk DMD gene carrier

and the other three male fetuses were DMD risk ones. The mothers of three probands were heterozygous.   Conclusion  STR polymorphism-based linkage analysis is suitable for DMD patients no matter who had not been found common deletion or not.