Fetal sex influences the accessibility of the placental chromatin to REST. REST targeted fewer sites in the female placental compared to that of male. REST bound to 7,254 common sites in both sexes but nearly 17-fold more number of sites in the male placenta compared to the female placenta. Overall design: Pooled sample from three biological replicates of day 15 placenta of male and female fetuses of wild-type (C57BL/6) mice were subjected to chromatin-immunoprecipitation assay for transcription factor REST followed by sequencing (ChIP-seq).