Which patients are suitable for single embryo transfer (SET)?

Deciding whether a patient should be offered single embryo transfer is a matter for the clinical discretion of the health practitioner(s) involved, and should follow the clinic´s protocol for minimising multiple births.

The British Fertility Society (BFS) and the Association of Clinical Embryologists (ACE) have recently issued professional guidelines on elective single embryo transfer (eSET). These guidelines can be found on the website of the journal, Human Fertility. Further information about these guidelines will appear on OneataTime soon. In the meantime you may also find the following suggestions helpful.

Whether the transfer of only one embryo is the right treatment for a particular patient depends on their prognosis for getting pregnant after IVF. The women with the best chance of getting pregnant after IVF are also at highest risk of conceiving twins.

Which are the relevant factors?

The factors that have been identified as being relevant are:

• The woman´s age.
• Her obstetric and gynaecological history.
• The number of previous failed IVF attempts.
• The woman´s ovarian response.
• The number and quality of embryos created.
• The availability of good quality embryos, including blastocysts.

However, although each factor is relevant, it is the overall prognosis that is important.

The importance of the overall prognosis

eSET is not just for the under 37s. The Human Fertilisation and Embryology Authority (HFEA) figures for eSET for 2004 and 2005 (live birth rates of 23.7% and 18% respectively, compared with the figures of 23.8% and 22.4% for the under 35s) also suggest that eSET can be performed successfully even in older patients (35–39 years) with good quality embryos (see embryo grading).

Equally, the number of previous failed IVF attempts needs to be taken into account when targeting single embryo transfer to the right patients. This is because the reasons that prevented successful treatment in the first two or three cycles of IVF are thought to also reduce the risk of twin birth in further cycles. This means that single embryo transfers are normally restricted to the first one or two IVF cycles.

Which criteria are applied at present?

Recent international eSET studies were carried out using the following criteria:

• Women under 34 who started their first in vitro fertilisation (IVF) / intra-cytoplasmic sperm injection (ICSI) cycle and had at least two good quality embryos.
• Women of all ages who had at least 4 good quality embryos and no more than one failed treatment cycle.
• Women under 36 who had at least 2 good quality embryos.