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The messenger RNA of the DNA methyltransferases DNMT3a and DNMT3b are expressed temporally in the endometrium across the menstrual cycle, as is the steroid hormone regulation of DNMT1, DNMT3a, and DNMT3b. This suggests that DNA methylation in endometrium is changeable during the menstrual cycle and potentially alters gene expression. (Fertil Steril (R) 2011;95:1522-5. (C) 2011 by American Society for Reproductive Medicine.)

Free to read at publisher's site. The endometrium undergoes morphological and functional changes during the menstrual cycle which are essential for uterine receptivity. These changes are driven by estrogen and progesterone and involve the fine control of many different genes-several of which have been identified as being epigenetically regulated. Epigenetic modification may therefore influence the functional changes in the endometrium required for successful implantation. There is, however, only limited information on epigenetic regulation in endometrium. We review the potential role of epigenetic regulation of key processes during the menstrual cycle and present our own findings following a preliminary study into global acetylation levels in the human endometrium. A changing epigenetic state is associated with the differentiation of stem cells into different lineages and thus may be involved in endometrial regeneration. Histone acetylation is implicated in the vascular endothelial growth factor pathway during angiogenesis, and studies using histone deacetylase inhibitors suggest an involvement in endometrial proliferation and differentiation. The processes of decidualization and implantation are also associated with epigenetic change and epigenetic modulators show variable expression across the menstrual cycle. Our own studies found that endometrial global histone acetylation, as determined by western blotting, changed throughout the menstrual cycle and correlated well with expected transcription activity during the different phases. This suggests that epigenetics may be involved in the regulation of endometrial gene expression during the menstrual cycle and that abnormal epigenetic modifications may therefore be associated with implantation failure and early pregnancy loss as well as with other endometrial pathologies.

To determine what impact conventional in vitro fertilization- embryo transfer (IVF-ET) has on twin pregnancy and obstetric outcome compared with spontaneous twin pregnancy, we performed a retrospective study of twin pregnancies in 1095 women (1059 spontaneous and 36 IVF -ET pregnan- cies). The maternal age of women receiving IVF-ET (34.25±4.86 yr.) was greater than that of those of spontaneous pregnancy. The gestational weeks of IVF-ET were significantly shorter than spontaneous pregnancy, but there was no significant difference in mean birth weight of 2 groups. The cesarean birth rate for IVF-ET pregnancies was 58.8%, which was relatively higher than that for spontaneous pregnancies. Prognosis for the babies was not significantly different between the groups.