Objective: The purpose of this study was to investigate imprinting patterns in first-trimester human placentas. Study Design: Using samples of 17 first-trimester and 14 term placentas from uncomplicated pregnancies, we assessed loss of imprinting (LOI) at the RNA level in a panel of 14 genes that are known to be imprinted in the placenta with the use of a quantitative allele-specific reverse transcriptase polymerase chain reaction analysis of those genes that contained readout single nucleotide polymorphisms in their transcripts. Results: There is significant LOI (ie, biallelic expression) in all 14 genes in first-trimester placentas. LOI was more variable and generally at lower levels at term. Although there is little difference in gene expression, the level of LOI is higher in the first-trimester placentas, compared with term placentas. Conclusion: Genomic imprinting appears to be a dynamic maturational process across gestation in human placenta. In contrast with prevailing theories, epigenetic imprints may continue to evolve past 12 weeks of gestation.

Original languageEnglish
Pages (from-to)391.e1-391.e8
JournalAmerican Journal of Obstetrics and Gynecology
Issue number4
StatePublished - Apr 2010


  • epigenetics
  • gene expression
  • loss of imprinting
  • placenta


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