The relationship between pregnancy outcome and smooth endoplasmic reticulum clusters in MII human oocytes

J. Otsuki, A. Okada, K. Morimoto, Y. Nagai, H. Kubo

Research output: Contribution to journalArticlepeer-review

151 Citations (Scopus)


Background: During ICSI, we occasionally observe pronucleus sized translucent vacuoles. We investigated why these vacuoles occur and determined the effect on pregnancy outcome. Methods. Translucent vacuole-positive oocytes and the corresponding cohort were examined by transmission electron microscopy (TEM) and histochemical staining with Dil and ER-Tracker. Stimulation methods, hormonal levels, patients' condition and grade of transferred embryos were compared between vacuole-positive and vacuole-negative cycles. Results. By TEM, we confirmed that the vacuoles were tubular-type smooth endoplasmic reticulum clusters (sERCs). Numerous small sERCs were also observed in the oocytes from the same cohort. Veeck's grades of transferred embryos were higher in sERC-positive cycles and fertilization rate was similar to those of sERC-negative cycles. However, in sERC-positive cycles, significantly lower pregnancy and higher biochemical pregnancy rates were shown. Serum estradiol levels on the day of hCG administration were significantly higher in sERC-positive cycles. Conclusions: The presence of sERCs is associated with lower chances of successful pregnancy, even in sERC-negative oocytes from the same cohort that are transferred along with the sERC-positive oocytes. High estradiol levels could be one of the causes of sERC formation.

Original languageEnglish
Pages (from-to)1591-1597
Number of pages7
JournalHuman Reproduction
Issue number7
Publication statusPublished - Jul 2004
Externally publishedYes


  • Biochemical pregnancy
  • High serum estradiol levels
  • Idiopathic infertility
  • Oocyte maturation
  • Smooth endoplasmic reticulum cluster

ASJC Scopus subject areas

  • Reproductive Medicine
  • Obstetrics and Gynaecology


Dive into the research topics of 'The relationship between pregnancy outcome and smooth endoplasmic reticulum clusters in MII human oocytes'. Together they form a unique fingerprint.

Cite this