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[Characteristics of IGF-II gene imprinting in twin placentas].

OBJECTIVE
To compare insulin-like growth factor II (IGF-II) gene imprinting in twin placentas with singleton ones and to determine whether imprinting was influenced by assisted reproductive technology, zygosity and fetal sex.


METHODS
One hundred and sixty cases of twin placentas and 42 cases of singleton ones were recruited. Allele-specific IGF-II expression was determined by reverse transcription-PCR combined with analysis of an Apa I-sensitive restriction fragment length polymorphism.


RESULTS
Although the incidence of IGF-II imprinting loss was higher in normal twin placentas than in singleton ones (20.6% vs 8.7%), there was no statistical significance. There were no significant differences between twins conceived by assisted reproductive technology and those conceived spontaneously (17.9% vs 24.4%), and between dizygotic and monozygotic twins (22.4% vs 16.7%). The incidence of IGF-II imprinting loss in placenta of female twins was statistically higher than that of male ones (26.4% vs 9.8%).


CONCLUSION
The risk of IGF-II gene imprinting loss is higher in female twins and has no relationship with assisted reproductive technology and zygosity.