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February 2012

ESHRE response to the Nature Medicine report on oocyte formation by mitotically active germ cells

29th February 2012 - A report published online by Nature Medicine on 26th February - from the group of Jonathan Tilly and colleagues at Massachusetts General Hospital, Boston, USA - proposed that the ovaries of reproductive-age women, similar to adult mice, possess rare mitotically active germ cells which can be propagated in vitro and can generate oocytes in vitro and in vivo.(1)

The study was widely reported in the press, with most publications suggesting that these ovarian stem cells "are capable of producing new eggs". Tilly himself was quoted by the Washington Post as saying: "Our current views of ovarian aging are incomplete. There’s much more to the story than simply the trickling away of a fixed pool of eggs."

Commenting on the paper for ESHRE, Dr Anna Veiga, the Society's Chairman, said: "The paper reopens the debate on whether oogonial stem cells exist, what their characteristics are in terms of pluripotency, and what role they have.
The data both in the mouse and human as recently published in Nature Medicine provide evidence for the existence of stem cells in ovarian cortical tissue, when isolated and tested for their properties and functionality. The cells possess characteristics of primitive germ cells, can be expanded for months and can generate structures similar to oocytes as determined by morphology, gene expression and haploid status. These cells were able to produce follicles and oocytes when injected into immunodeficient mice.

"There are still questions to be resolved with respect to the role of these cells in the normal reproductive life span, whether they could be used for fertility preservation or to extend reproductive life. Even though they constitute a very relevant contribution to the field, the results published by the group of Tilly need to be reproduced by other groups to be confirmed."

1. White YAR, Woods DC, Takai Y, et al. Oocyte formation by mitotically active germ cells purified from ovaries of reproductive-age women. Nature Med 2012; doi:10.1038/nm.2669

January 2012

ESHRE response to The Lancet report on the number of embryos to transfer

12th January 2012 - A prospective analysis of 124,148 IVF cycles (and 33,514 live births) published in The Lancet today provides further evidence on the association between the number of embryos transferred and live birth according to patient age.(1)

As indicated by earlier studies, the transfer of two embryos in patients both older and younger than 40 years led to higher birth rates than with single embryo transfers; however, live birth rates did not increase with the transfer of additional embryos, although the risk of adverse perinatal outcomes did increase. As a result, the investigators conclude that the transfer of three or more embryos should be avoided in IVF. The decision to transfer one or two embryos, they add, should be based on prognostic indicators such as age.

ESHRE's own policy on reducing the incidence of multiple pregnancies in IVF was set out clearly in its position paper on Good Clinical Treatment in Assisted Reproduction in 2008, in which single embryo transfer (SET) in selected groups of patients was advocated as "the only effective means of lowering the rate of twin pregnancies".(2)

However, ESHRE also made it clear that such SET policies can only be applied successfully in combination with high quality embryo selection and a good cryopreservation programme. The latter will ensure that cumulative birth rates with SET are just as high as with two-embryo transfers from a single cycle of oocyte retrieval, with a far lower likelihood of twin pregnancies. Success rates will also depend on the selection of good quality embryos with the potential for implantation; ESHRE's current trial of oocyte screening by comparative genomic hybridisation (CGH) will provide important new evidence.

Meanwhile, ESHRE remains committed to the practice of single embryo transfer as set out in its 2008 Good Clinical Treatment in Assisted Reproduction paper and, as The Lancet editorial also makes clear, to the concept of one healthy baby at a time.

Article in The Lancet

ESHRE position paper on Good Clinical Treatment in Assisted Reproduction

October 2010

Francoise Shenfield, Coordinator of the ESHRE Task Force 'Cross Border Reproductive Care': We need a code of practice for cross-border reproductive care, BioNews