Statement on embryo transfer study

A multiple birth is the single biggest risk of IVF for both mothers and babies. However, it is a risk that can be avoided by the transfer of one embryo to those patients who are most likely to have twins.

Research published in The Lancet has suggested that the transfer of two embryos in IVF is more likely to lead to a live birth than the transfer of one embryo. However, the transfer of two embryos is more likely to lead to complications such as multiple births, premature births and low birthweight.

These findings echo our own data analyses, which show that whilst two-embryo transfer results in a slightly higher birth rate, the chance of having twins is significantly higher. As the representatives of IVF professionals, patients and neonatologists on our Multiple Births group agree, patients must weigh the chance of a live birth against the serious risks associated with a twin pregnancy and birth, both for themselves and their babies.

Evidence shows that clinics can maintain overall live birth rates, whilst practically eradicating the risk of multiple births, by carefully selecting the most suitable patients for elective single embryo transfer and by including subsequent frozen embryo transfers in a complete cycle of treatment.

Suggestions in the press that The Lancet study findings challenge the HFEA’s policy on multiple births are incorrect. The authors of the study suggest that the decision about whether to transfer one embryo or two in individual patients should remain a clinical decision. This is consistent with our policy which sets a maximum multiple births rate, but leaves clinics to draw up their own patient selection criteria in order to meet that target.

Professor Scott Nelson, co-author of The Lancet study, said ‘Individualising the number of embryos to be transferred is critical and the HFEA policy on multiple births allows for this. In women under the age of 40, transferring two embryos carries a major risk of twins and the babies being born prematurely with a low birth weight. This can be avoided by replacing embryos one at a time. In women over 40 the chance of becoming pregnant is lower and so two embryos can be replaced without the same risk of complications. We also showed that transferring three embryos at any age does not improve the chance of having a baby.’

This approach is working: across the IVF sector in the UK, the rate has reduced from 24% (before the policy was introduced) to 18%. Clinics are currently working to bring the rate below the current target of 15%.

The Lancet study also suggests that transferring three embryos is no longer appropriate for any women. HFEA guidance does not allow the transfer of three embryos to women under 40. We will study these findings further over the coming months to see whether our guidance on three-embryo transfers should be revised.

For further information about multiple births, see One at a Time


Notes to editors

  • The HFEA is the independent regulator for IVF treatment and embryo research. Our role is to protect patients and defend standards, to drive improvement in the treatment and research sectors and to provide information to the public and policymakers about treatment and research. We are not an economic regulator.
  • The HFEA was set up in August 1991 as part of the Human Fertilisation and Embryology Act 1990.  The HFEA’s principal tasks are to license and monitor clinics that carry out in vitro fertilisation (IVF), artificial insemination (AI) and human embryo research. The HFEA also regulates the storage of gametes (eggs and sperm) and embryos. See for further details.

For further information please contact the HFEA press office on 020 7291 8226 or email 

Page last updated: 12 January 2012

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