Discordant Growth of Monozygotic Twins Starts at the Blastocyst Stage: A Case Study

Stem Cell Reports. 2015 Dec 8;5(6):946-953. doi: 10.1016/j.stemcr.2015.10.006. Epub 2015 Nov 12.


Discordant growth is a common complication of monochorionic/diamniotic pregnancies; in approximately 50% of cases, the cause is unknown. The case presented here suggests that discordant growth of monozygotic twins could start during preimplantation development. Two inner cell masses (ICMs) within the same blastocyst may originate in uneven splitting of a single "parental" ICM, or the two ICMs may be formed independently de novo. We studied the transcriptomes of two morphologically distinct ICMs within a single blastocyst using high-resolution RNA sequencing. The data indicated that the two ICM were at different stages of development; one was in the earliest stages of lineage commitment, while the other had already differentiated into epiblast and primitive endoderm. IGF1-mediated signaling is likely to play a key role in ICM growth and to be the major driver behind these differences.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blastocyst / cytology*
  • Blastocyst / metabolism
  • Embryo Culture Techniques
  • Gene Expression Regulation, Developmental
  • Humans
  • Insulin-Like Growth Factor I / metabolism
  • Signal Transduction
  • Transcriptome*
  • Twins, Monozygotic / genetics*


  • IGF1 protein, human
  • Insulin-Like Growth Factor I